Kristin walks through the parish grounds with the priest who is arranging Ethan's funeral. He asks Kristin why she wants Ethan cremated and she replies that she always thought fire was purifying and wants Ethan to be cleansed. He asks where Ethan's final resting place is to be and Kristin tells him that it will not be underground; his ashes will be scattered on the water. The priest finally asks Kristin which faith she belongs to and Kristin replies that she has no faith.
Further ahead, Nick comes up to Derek and tells him that the police have ruled Ethan's death as accidental and will release the body soon. He asks Derek how Kristin is coping, however Derek hasn't spoken to her yet, but he can imagine. They approach Kristin and Derek gives her his condolences, begging her not to let Ethan's death destroy her as that is what Horton wants - to pull them apart. Kristin tells him that Horton has succeeded. Derek begs her to be strong, but Kristin retorts that Ethan is dead and how much stronger does she have to be. Nick says it isn't for Derek's benefit but for hers. Fighting back tears, Kristin says she should have been with Ethan instead of doing Legacy business. Derek begs Kristin not to do this, but Kristin adamantly tells him that the Legacy can go to Hell and walks away. Nick tells Derek that Kristin will need time if she is to return to them. Derek comments that Horton won't give them time - he will attack again and they have to be ready. Nick tells him it won't be easy as any help they may have had in Boston is either dead or missing. Derek insists they take the fight to Horton, but Nick points out they have to find him first.
An angry Mordecai confronts Horton, stating that the boy should have been his. Horton tells him to be patient as they have succeeded in driving a wedge between Kristin and Derek. Mordecai demands to know why Horton is so obsessed with Derek and Horton replies that Derek is capable of destroying them all. The Legacy must cease to exist. Mordecai tells Horton that he has other goals in mind, but Horton tells him that his goals are not important and the only thing that matters is what 'it' wants. Mordecai realizes that Horton is serving someone and asks whom, but Horton tells him all he needs to know is that he will be free and not be limited by conscience or compassion. Mordecai asks about Kristin and says he needs her, however Horton emphasizes that Kristin must live for now as he needs her.
Philip lights some candles and Nick asks him if he ever looked back after leaving the Legacy. Philip says he missed the friendship and he missed Nick, Derek and the others, however the violence and the constant doubt were not for him. Nick comments that he was never a big fan of that part himself, but it goes with the territory. Philip says they are both trying to save the world, only he is doing it one soul at a time and that he was never too fond of driving stakes through hearts. Nick laughs and says it grows on you. Getting serious, Nick tells Philip that they really could use his help, but Philip refuses to abandon his parish. Resigned, Nick accepts Philip's answer and says he needed to know where they stood. Getting up to leave, Nick asks Philip to light a candle for them and shakes his hand. Philip contemplates the candles, looking troubled.
Boston Legacy House
Derek is sitting in front of a monitor, pinpointing various spots on a grid map of the city, as Nick comes back. Looking up, Derek asks how his chat with Philip went. Nick tells him they are on their own. Derek tells Nick that he has been going through Jane's files and highlights an area on the map where the most recent disappearances occurred. The area also ties in with Horton and Ethan's death. Nick remarks that Horton is too smart to stay hidden in the same tunnels. Derek agrees, but tells Nick that he was thinking more about Mordecai Church. Nick points out that they don't know if the guy even exists or even if Horton would team up with him. Derek reflects that Horton is vulnerable and may need help to destroy the Legacy. Nick decides to check out the area where Ethan was killed to try and find an entrance to Mordecai's tomb.
Kristin pours Ethan's ashes into the water, as Philip stands to the side. As they turn to leave, Kristin asks Philip if he ever wonders what he'd have done if he hadn't become a priest. Philip admits that the thought has crossed his mind. Kristin tells him that sometimes she sees the faces of people and wishes that she had their lives. Philip wryly comments that she should have seen the face of the girl he was engaged to when he told her that he was going to become a priest. Kristin asks if he broke her heart and Philip says she got her own back by breaking his nose. Kristin laughs. Philip tells her for every choice they make in life, something else has to be given up. Kristin asks how do you know it is worth it and that they both could have been living ordinary lives. Philip replies that they are not living ordinary lives and Kristin adds that they never will. Kristin looks sad and Philip asks her if she wants to tell him something. She shakes her head, leans over to kiss Philip on the cheek and says she was just thinking about 'what might have been'. She smiles and says she hopes the kiss didn't break any of his vows. Philip laughs and says it will have to last him ten years.
As they walk away, Mordecai appears from behind a pillar and watches them.
Nick and a security man enter the building; the security guy asks if Nick is sure this is the building he wants to see. Nick assures him that his associates are very particular about the types of buildings they invest in. The security man thinks he's looking in the wrong part of town since the tunnels are right below them and the whole building shakes when the excavation machines get going. Nick hands the security guy some money and asks him to take the rest of the day off so he can investigate the building further. The security guy hesitates, and then takes the money, leaving Nick alone.
The elevator begins to rise and Nick pulls his gun, taking cover behind a pillar. The elevator stops on Nick's level, but no one gets out. Nick moves from behind the pillar, just as the elevator begins to move, continuing its upward journey. Nick peers over the edge of the shaft, then watches the elevator move upwards. Suddenly sensing someone behind him, Nick turns to see Horton standing there. Nick pulls his gun, but Horton hits him with a blast of energy that knocks him off his feet and sends the gun down the shaft. Nick tries to grab the gun, but is too late. He stands and faces Horton, who reminds him that bullets cannot harm him. Nick responds that he knows they hurt like hell and he loves seeing the look on his face. Horton calls him "an arrogant little worm" and tells him that he wanted to wait until later to kill him. Nick moves closer to the shaft edge and reaches a hand up to catch a piece of dangling rope. Just as Horton is about to blast energy at him, Nick jumps over the edge, landing heavily in the shaft below, but managing to retrieve his gun in the process. He points it upwards, but there is no sign of Horton.
Later, Nick painfully props himself up against a wall. He hears a sound and aims his gun only to see Derek with his hands raised. Derek asks if he should have worn a bell and comments that Nick is very jumpy. Nick sarcastically puts it down to too much caffeine and asks why it took Derek so long to get there. He gets to his feet with a struggle. Derek tells him he checked out the lower level and found a shaft descending directly into the earth. Nick tells Derek that the city has been drilling holes to check the foundations of the buildings and that there could be dozens. Derek notes that Horton can come and go as he pleases and they will never find him that way. He asks Nick how his leg is, and Nick replies that a 30-foot fall is better than drop training in the Seals, but he was hit with a strong jolt. Derek reminds him that Horton has to be close if his touch is to be lethal and that someone else probably caused the marks on Jane and the others. Nick muses that Horton is getting help and Derek remarks that they could use some too. Nick reminds him that Jane is dead, Philip has "hung up his spurs" and there's nobody else to call on. Derek says it has to be someone already familiar with the case and who knows Boston. Catching on, Nick grins and tells Derek that he is out of his mind if he is thinking about talking to Kristin. Derek pats Nick on the shoulder and tells him that he was thinking Nick would talk to her instead.
As they leave the building, Horton appears from the shadows and then doubles over in pain. There is a fiery blast and Horton yells that he needs more time. Supernatural fires burn around Horton and a deep voice reminds him that he had help and still accomplished nothing. A young boy with a hideous face and long, forked tongue appears and Horton insists he will kill his enemies in his own way. The boy tells him he'd better succeed or he knows what will happen, indicating something behind Horton. Horton turns and sees a man hanging upside down on a cross. Terrified, Horton pleads with the boy not to do that to him again. The boy's eyes glow red and he orders Horton to defeat his enemies. Laughing evilly, he disappears. The man on the cross begs for Horton's help.
Nick and Kristin walk through the falling snow. Nick reminds Kristin that Horton is still out there and she argues that revenge won't bring Ethan back. Nick says that getting Horton may make her feel better - it would for him. Kristin tells Nick that she doesn't have that killing instinct and that if she had left the Legacy when she first thought about it, Ethan might be alive. Instead she was trapped by duty and honor and the belief that she could save the world. Nick tells her that there are worst things to believe in and Kristin says not when it costs the lives of those you love. Nick reminds her that Chris Corman is still missing and she can either run away from the situation or stay and help. Disappointed, Kristin tells Nick that she thought he would have understood her feelings. Nick reminds her that he does - he lost his father and his brother - not because of what the Legacy believes in, but because of what it fights against. He tells Kristin that she shouldn't quit and should do whatever it takes to win. Kristin asks why and Nick replies that that is all there is. Kristin looks thoughtful.
Chris Corman has been bound to a makeshift cross and Mordecai demands he renounce the Legacy. Chris painfully cries that he will, but that doesn't please Mordecai - Chris gave in too easily and is not a worthy opponent. Horton approaches and Mordecai accuses him of not telling the truth when he said the souls of the Legacy were stronger and would free him. Horton tells him that not all the souls are like that, but there are others on whom Mordecai should concentrate. Mordecai absorbs Chris's soul.
Nick and Derek approach one of the shafts leading underground. Nick tells Derek that he kept his receiver on in case he got a signal from Chris's locator - when he received a signal he traced it here. Derek asks him if he has the crossbow and Nick takes it out of his backpack. At that moment, an engineer approaches and looks down the shaft, wondering what Nick and Derek are doing. Nick tells him that they are from Pest Control and are hunting for rats. Derek adds that they are big rats. The engineer looks at them then moves away. Nick looks at Derek, trying not laugh. They both descend the shaft into the tunnels and progress along it, following Chris Corman's signal. The signal is becoming weaker and Nick eventually finds it half buried in the tunnel floor. Derek surmises that Corman dropped it, hoping it would be found. Nick shines the torch along the tunnel and stops when he comes across Corman's body. Nick rushes over and sees that Corman has been bound upright to the tunnel wall; he takes his pulse, confirming that he is dead.
Nick notices that there are letters carved into Corman's chest and wonders if it is a code. Derek eventually recognizes it as Latin written in reverse: EANRETEA XUL (Lux Aeternae), which means Perpetual Light and is part of the Catholic Mass for the Dead. Nick asks why it is written in reverse and Derek tells him that writing the phrase in reverse invokes the power of the words. They realize that someone hoping for eternal light has sacrificed Corman. In disgust, Nick reaches up to cut Corman down, but stops when he notices that a word has been scratched into the wall beside Corman's hand: CHURCH. Nick muses that Corman must have done it before he died and Derek says that somehow Mordecai Church has returned from the dead and is working with Horton. Angry, Nick cuts Corman down.
Boston Legacy House
Nick is working at the computer when Kristin walks in, saying she got his message. Nick says he wasn't sure if she would come. Kristin looks at him and asks if it is about Chris. Nick tells her they found him dead in the tunnels. Kristin asks if it was Horton and Nick tells her that it was probably Mordecai Church and he was also responsible for Jane and the others too. Nick says he's sorry about Chris. Kristin starts to tell him that she thought about what he said before and Nick interrupts saying he was out of line, but Kristin tells him that he was right. She wants back in and wants to find Horton and Mordecai, but not for the Legacy - for Ethan. Nick nods, understanding. Kristin tells Nick about Suzanne, Ethan's girlfriend, and her involvement with a religious group lead by a man calling himself "The Doctor". Nick comments the city has "more flakes than a box of laundry soap". Kristin agrees that he is an unusual character, but he said he'd look out for Suzanne and maybe he has found out something by now. Nick reminds her that revenge is only good if you are around to enjoy it. Kristin promises to be careful.
Mordecai tells Kristin that he hasn't seen Suzanne. Kristin tells him that he must be aware that several people in the area have gone missing. Mordecai asks if she knew Suzanne well. Kristin says that she was a friend of her brother's and she sadly looks at the floor. Mordecai asks if Ethan knows where Suzanne might be and Kristin shakes her head. Mordecai reaches over, gently grasps her chin and raises her head. He tells her that he senses she is in great pain and she radiates feelings of pain and failure. Kristin closes her eyes. She tells him that Ethan died recently - he was murdered by Horton. She asks Mordecai if he knows him, and Mordecai says he's heard the name. Kristin asks him to inform her if he hears anything about him. Mordecai tells Kristin that if she stays he can return the peace she has lost. Kristin declines and asks if he can perform miracles. As she leaves, Mordecai mutters to himself that he's working on it.
Boston Historical Society
The elderly curator, Mr Penfold, shows Derek into a room and tells him that Jane was one of their rare patrons, as few people know they exist. Derek agrees that Jane had an interest in the arcane and Penfold says Derek must also be a member of that Looney Foundation which greatly amuses Derek. Derek asks if Penfold knows anything about Mordecai Church and Penfold states that they don't get a lot of requests for information on him since people would rather forget. He goes over to a cupboard and pulls out a wooden box, which he places on the table in front of Derek. Derek opens it and reveals an array of old medical instruments. Penfold tells Derek that Mordecai was a scholar and a medical doctor. Derek reaches into the box and pulls out a wickedly sharp knife, commenting that they look more like instruments of torture. Penfold tells Derek that a lot of Mordecai's followers either went missing or turned up dead and people believed Mordecai was in league with the devil. Derek pulls out a drawer in the front of the box, revealing more instruments. Derek asks Penfold what other evidence they had against Mordecai. Penfold reveals that Mordecai was caught in the act and sketches were made. Going over to a cabinet, Penfold takes out an old book and opens it. A series of drawings depict Mordecai's human dissections and the right page has a sketch of Mordecai himself. Derek asks what happened after the trial and where Mordecai was buried. Penfold tells him that he's like to know too, as the records were confiscated. Derek guesses they were confiscated by the Catholic diocese and asks if he can borrow the book for a while.
Horton asks Mordecai if Kristin really expects him to help her find Horton. Mordecai says he can be very persuasive, but Horton tells him not to flatter himself. Mordecai tells Horton that he is growing tired of waiting and Horton says that would be a mistake, as Mordecai still needs him. Mordecai says he is growing stronger with every soul he takes and won't need him much longer. Horton asks him what part of 'being damned' doesn't he understand. He says Mordecai can go on taking souls without ever gaining his freedom - even some Legacy souls won't be enough. He asks Mordecai if he has touched Kristin and felt the essence of her power. She is the one who can set them free, and then they both will have what they want.
Boston Legacy House
Kristin stands behind Jane's desk, holding the dagger that belonged to her father. Nick comes in, seeing she is deep in thought, he offers to come back. Kristin tells him that she was just cleaning Jane's desk and that the knife belonged to her father. Jane had wanted to give it to her before her death. Nick says Jane cared for Kristin very much. Kristin smiles and picks up a photo of herself and Jane, she passes it to Nick. Nick asks if she learned anything from The Doctor and Kristin replies that while he knew nothing about Suzanne, he seemed to know what Kristin was feeling. Nick asks if he 'feltí anything about Reed Horton and Kristin says he felt the name was familiar and he would let her know. Nick tells her he is going to call the police to find out if they have any new information on the missing people.
Philip is sitting in a pew comforting the Cavanaugh family - Beth's parents. He tells them not to give up hope of finding her. At that moment he sees Derek walk into the church and he excuses himself, telling them he will visit them at home later. Derek leads Philip away.
Boston Legacy House
Kristin's phone rings and she agrees to meet the caller, as she scribbles on a pad.
Philip insists that he held nothing back and that priests were often observers during trial. Derek points to the book he borrowed from the Boston Historical Society and tells Philip they were more than observers. The trial records clearly illustrate the involvement of Catholic priests. Philip reads the names of the monsignors present at the trial and tells Derek that they were not members of the Boston community. Derek tells him they were sent from Rome, but they were witch hunters, not observers. A secret group of priests trained to deal with the black arts. They were there to decide on Mordecai's punishment. Philip notes there is no record of the punishment and that the records are missing. Derek tells him that the records were confiscated by Philip's order. Philip is stunned. Derek tells him that he has the chance to rectify that mistake.
Kristin meets Mordecai Church and he tells her that he knows Horton's whereabouts. He leads her to a shaft and tells her he met a girl who had been held by Horton in the tunnels. She escaped and she believes that Suzanne is still alive down there. Kristin tells him that she has to tell her colleagues, but Mordecai convinces her there is no time and she should go with him now.
Boston Diocese Archives
Philip bluffs his way into the archives, introducing Derek as Father Damian. They search for the confiscated files and Philip comments that Catholics have almost as many secrets as the Legacy. Philip finds the sealed records and Derek tells him to break the seal of the container. Horrified, Philip tells him that he would be breaking his vows. Derek grabs the container and smashes it against the table, revealing two scrolls. The first scroll reveals that Mordecai was never executed but was buried alive in the catacombs. Philip notes the phrase: TENEBRAE AETERNAE - Darkness Forever† - that was engraved on Mordecai's tomb. Derek says the remains of his victims were buried around him as part of the curse, imprisoning his soul forever. Philip asks why Mordecai deserved such a terrible punishment and Derek pulls out the old book, showing Philip the sketches of the dissections. Philip is disgusted, but he notices the sketch of Mordecai and tells Derek that he is the street preacher called The Doctor.
The other scroll is opened to reveal a map of the catacombs and Derek realizes it could lead them to Mordecai's tomb. The map has the words: SUPERA OMNIA MONSTRA on a section and Philip declares they should be able to find it easily enough.
Derek calls Nick and tells him they know the whereabouts of Mordecai's tomb and that Mordecai is calling himself The Doctor. Nick, recognizing the name, tells Derek they have a problem. Kristin is with him.
Nick, Derek and Philip arrive at the shaft, which they believe will lead them to Mordecai's tomb. Nick pulls back the iron grating and they descend. Down below, Derek comments that the Catholic Diocese must have believed the tomb would never have been found this far down. Nick dryly points out that they didn't figure on public transit. He hands Derek the crossbow and warns him that it has an explosive head. Nick hands Philip a gun, but he refuses it, saying he has a weapon. Derek and Nick look at each other, puzzled, and ask him what it is. Philip replies that Mordecai was damned by a Latin phrase and he is hoping to use it again. Nick grumbles: "Gotta love the Irish. Guy goes to a gunfight armed with a dead language." They head off into the catacombs.
Further ahead, Kristin and Mordecai walk through the tunnels and Kristin comments that they have been walking for a long time. Mordecai assures her they are nearly there. They enter the tomb and Kristin says it must have been there for ages and appears to be empty. Mordecai states that it isn't empty and asks if she can feel 'them'. He strikes a match and lights a torch, as Kristin moves closer and asks who. He replies - the unquiet spirits who cry for revenge and justice. He lights another torch and tells Kristin that he has had to listen to them for 200 years. Suddenly, Kristin realizes that he is Mordecai Church and she raises her father's knife. Mordecai smirks and tells her it may not work on a being like him. Kristin tells him it worked for her father and they'd soon find out for sure. Mordecai says he's disappointed in her and Kristin says the feeling is mutual. She asks him about Suzanne, Beth and the others. Mordecai tells her they finally served a useful purpose. Kristin asks what he intends doing with her and Mordecai tells her she is special - the last "bastion of goodness" and his passport to freedom. Kristin asks him where Horton is and Mordecai indicates behind her and says to ask him herself. Kristin whirls around, but Horton grabs her arm, forcing her to drop the knife. He asks Kristin if she wants to kill him and she spits in his face. Horton informs her that she won't be joining her brother since Mordecai is going to take her soul. He pushes her backwards into Mordecai's waiting arms and Kristin blurts out that the others will find him. Horton grabs her by the chin and says he counting on it. He looks at Mordecai and says, "Bon appetit", before leaving. Mordecai tells Kristin that it is time to meet her Maker. She cries out in pain as he grabs her head.
Nick, Derek and Philip hear the cry and follow it. Derek stops when he sees Horton at the end of another tunnel - he follows him.
Mordecai has his hand on Kristin's scalp and is absorbing her soul, but Kristin is fighting him. Mordecai increases the pressure and Kristin screams. At that moment, Nick and Philip come running into the tomb and Nick aims his gun at Mordecai. Mordecai tells them they are too late and that he could easily kill Kristin instead of taking her soul. Kristin begs Nick to shoot. Nick aims at the wall and fires. A large chunk of rock is blown away and Mordecai, startled, releases Kristin. Mordecai turns to Nick and uses supernatural force to throw him across the tomb. He lies on the ground, stunned. Philip holds up a cross and walks steadily towards Mordecai, chanting. "Tenebre Aeternae - Darkness Forever." Mordecai recoils back. Philip continues walking forward, saying, "Supera omnia monstra!" (Vanquish all monsters). Mordecai staggers further back, holding his middle in pain. Hunched over, he grabs a metal pike and lunges towards Philip. However, at the last minute, Kristin throws herself in front of Philip and is stabbed deeply in the back. Philip lowers her gently to the ground. Nick recovers and begins blasting at the wall behind Mordecai. Light pours out of the cracks and the spirits of Mordecai's victims attack him. Mordecai falls further through the gap in the wall - there is a flash of light and he's gone. Nick rushes over to Kristin and she manages to tell him that Horton is still there. Nick grabs the crossbow and runs off. Kristin slumps against Philip's chest.
Derek shines his flashlight through the tunnels, searching for Horton. He hears a sound to his left, as he turns Horton grabs him, disarming him. Derek tells Horton that if he wants to kill him he should get it over with, but Horton smugly replies that he is already doing it by killing everything that Derek loves until there's nothing left. As he moves closer to Derek, Derek pulls out a knife and plunges it into Horton's gut. Horton doubles over in pain and Derek pushes him back. Nick arrives and yells at Derek to take cover. He aims the crossbow and hits Horton who disappears in a fiery explosion. He is transported to Hell, where the hideous demon child pins him upside down to a cross for all eternity.
Nick and Derek rush back to Kristin who is barely clinging to life. Derek clasps her hand and tells her that Horton is gone. Kristin remarks that they have won and Nick urges her to hang on and to stay with them. Kristin's head slowly falls to the side - she's dead. Nick rubs his face in despair and Derek sadly kisses her hand.
"I wished to leave the Legacy and its battles forever, but it seems our paths are linked by some unbreakable bond. As I write this I'm about to go after Ethan's killer - to destroy him for once and for all. If you are reading this then the worst has come to pass. I want you to know this - whatever happens in the next hours - I'm not afraid. If there is such a thing as destiny then perhaps this is mine. God bless and keep you all. Kristin."