Karen Morgan (the succubus from season two's Black Widow) sits in the bar, opposite a young man who is very attracted to her. Karen suddenly gets to her feet and tells him she has to leave. Bewildered, the young man watches her walk away, only to be stopped by Bill Davies at the bar. Davies asks Karen where she's going and she whispers something in his ear. She leaves and the man follows her eagerly.
Karen and Davies get on a boat and begin to kiss passionately. Karen suddenly breaks away from him in pain. Davies, concerned, asks if she is okay. She assures him she'll be fine as she grabs him roughly. Davies tells Karen that he really needs this and she replies not as badly as she does. She kisses him roughly and ribbons of energy snake out of her mouth and eyes, linking with Davies' eyes and mouth. Davies screams in pain as his life is drained away.
Legacy House - 4 weeks later
Nick returns from his morning run and Rachel informs him that his friend, Mike MacCreedy (see Devil's Lighthouse) called. Nick asks how he seemed and Rachel says he sounded really well - he's met a girl and is sorting out his life. Nick is surprised to hear Mike's met someone as Mike has a tendency for violence when drunk. Rachel tells Nick that Mike may not be drinking anymore and urges Nick to see him. Nick is very reluctant, but Rachel tells him that Mike sounded excited and really wanted to talk. At that moment, Rachel's pager buzzes and as she responds, she tells Nick that Mike's number is by the phone and he should call.
Nick pulls up in front of a house on the shorefront and Mike rushes down the steps to greet him. They hug warmly and Nick asks Mike when he moved. Mike reveals he bought the place a couple of months ago but it needs a lot of work. Nick teases him about being domesticated and Mike puts it down to meeting Anna. He tells Nick that Anna has really turned his life around and that she is a very special lady whom he'll meet at dinner. They go into the house.
Mike and Nick are seated at a table and Mike tells him that Anna is the type of woman you fall in love with at first sight. Nick notes that Mike is drinking coffee and Mike informs him that coffee is the strongest drink he has had in four weeks. Nick warns him to be careful and to take things slowly.
At that moment, a blonde woman walks into the restaurant with her back towards the table. Mike spots her and points her out to Nick, calling her name. Anna turns round - it is Karen Morgan. As she walks towards them, Nick gets a strange look on his face, like he knows her but can't quite place her. Mike gets up to greet Anna with a kiss and a hug, as she turns to say hello to Nick. Nick is still staring at Anna much to Mike's amusement. Nick shakes himself out of his reverie and apologizes to Anna, telling her that she really looks like someone he once knew. Anna laughs and says she must have one of those faces as people say that all the time.
Downtown - later
A guy chases his girlfriend and pushes her against a wall, yelling at her. Just as he's about to hit her, Karen grabs his arm and tells him to leave her alone. He turns and demands to know who she thinks she is. Karen tells him that she is just looking for a party and asks if he is up to it. Interested, the guy tells her he knows where there is a party 24/7 and indicates towards a dark spot in the alley. Karen grimaces in pain and he asks if she needs anything. Karen says she only needs him and to lead the way. They leave the girl, Julie, behind.
In the alley, Karen and the guy start kissing and she asks him if he's going to be rough with her. He promises to be good just as the energy ribbons snake from Karen's eyes and mouth. He moves back in shock and pulls a knife, cutting Karen on the arm. Karen angrily pulls him towards her and pushes him against the wall. She drains his life.
Rachel answers her phone. It is Detective John Royce of the SFPD requesting her help with a case; he tells her that he got her name from Frank Karmack who informed him that she worked on 'delicate' cases. Rachel agrees to meet with him in the afternoon once she has finished a patient appointment and hangs up.
There is a knock at the door and - it is Karen Morgan, introducing herself as Anna. Rachel, obviously expecting her, invites her in and gets the same strange look on her face as Nick did at the restaurant. Anna stands in front of a shelf that holds a picture of a smiling Nick and Rachel. She smiles at it and turns towards Rachel, asking if she stares at all her patients that way. Rachel tells her there is something really familiar about her, to which Anna replies that they may have met in a previous life. Rachel invites Anna to sit down and asks if she was recommended by a mutual friend. Anna confirms it but says he wishes to remain anonymous. She removes her coat as Rachel tells her she can clear a slot that evening for a full appointment and in the meantime they can cover some groundwork. Anna tells her that she has been out of touch for a long period and wants to start living again to satisfy her 'needs and desires'. As she says this she begins to have flashbacks to the time she spent with Nick (see Black Widow). Rachel asks her if there is somebody in her life and Anna says there was and it was very special, again thinking of Nick. Anna then tells Rachel she had to go away as she remembers being dragged from the pier into the water. Rachel asks if she wants to restart the relationship and Anna confirms that she wants to know how to get him back. Rachel advises her to be herself, but Anna scoffs and says she doesn't know that person. She gets up and paces the room, very agitated. Rachel, watching her closely, tells her to find the part of herself that she likes the best and to build on it. Anna smiles and tells Rachel that is good advice, as she turns and smiles at Nick in the photo.
Nick is sound asleep on the sofa. Anna stands over him and leans forward, nudging him awake. Startled, Nick asks the time and is surprised at how late it is, saying he and Mike were talking until 4 in the morning. Anna remarks that Mike didn't get to sleep in as he had to be at the boat yard for 6 a.m. Nick comments that that's the price of having a steady job and asks Anna why she's there. Anna says she has an idea for helping Mike with the house.
Anna and Nick descend the stairs into the basement, searching for paint. Nick tells Anna that Mike wants to fix up the house for her. Anna shrugs and says Mike lives in his own fantasy world and that they aren't serious. They are just friends and she doesn't love him. Nick looks surprised and tells Anna that Mike is in love with her. He turns towards a locked closet and heads to it in search of tarpaulin covers. Anna quickly stops him, saying the tarpaulin covers are in the cupboard upstairs. Nick moves away from the closet and Anna looks at it in satisfaction.
Detective Royce thanks Rachel for coming and invites her to sit down. He smiles at her, obviously liking what he sees. He shows her a plastic evidence bag containing a knife and tells her that it was found in an alley the previous night. The alley is a known stomping ground for a street hustler who is now missing. Rachel asks if they think the hustler was killed with the knife. Royce informs her that they can't tell without a body. Confused, Rachel asks why it is a homicide case if there is no body. Royce tells her he got the case because this is the second person that has disappeared under unusual circumstances. He shows Rachel a photo of a sailor, Bill Davies, saying he left a bar with a woman a few weeks ago and was never seen again. He tells Rachel a witness saw Davies leave the bar with the woman and he saw a bright light on the dock. Royce hands Rachel a photo of the street hustler (it is the violent boyfriend) and tells her a passerby heard him scream and saw a bright light in the alley. Two similar occurrences show that something odd is happening. Turning to the knife, Royce explains that a lab analysis determined the blood had human qualities but wasn't like anything they had seen before. Rachel asks to take the knife for testing and Royce agrees, saying he'd appreciate any help the Foundation can provide. Rachel tells him he'll be the first to know if she finds anything out and leaves. Royce watches her leave, a small smile on his face.
Nick and Anna are painting the lounge. Anna is painting the ceiling, but stops when she notices Nick staring. Nick says he was admiring her painting skills, and asks if she has done this professionally. Anna laughs and says not likely. Nick asks her what she does for a living and Anna tells him she is between jobs until she gets her life sorted out. Nick points out that it sounds like there was a man in the picture. Anna admits she was deeply involved with someone but she had to leave before it had a chance to blossom. Nick takes a drink of water out of a bottle and tells Anna that maybe it was meant to be. Anna smiles and tells him she thinks so. Just then some paint drips on to her hand and Nick, laughing, tells her it's raining. Anna laughs and wipes the paint on Nick's cheek. He wrestles with her and ends up pulling her into his arms. They stop laughing and look into each other's eyes. Just as they are about to kiss, the front door opens. Mike walks into the room, as they separate quickly. Mike looks at them with a serious expression and says he shouldn't have left them alone together, as he points to the painted walls. Nick and Anna laugh guiltily. Mike tells them he has take-out, but Nick decides to head back to the city. Disappointed, Mike says he thought Nick could stay a couple of days. He tries to persuade Nick to stay but Nick is very reluctant. Anna tells them she has an appointment in the city and Nick should stay and eat with Mike. She kisses Mike on the cheek and leaves. Mike comments that Anna is weird sometimes and needs her space. A troubled Nick just agrees.
Anna paces up and down, telling Rachel that her guy needs some space. Rachel asks Anna if she was rejected by the man. Angrily, Anna denies it, saying that he is just confused about what he wants and she doesn't know how receptive he would be to getting back together. Rachel asks how Anna feels about that. Anna says she is depressed and angry. Rachel asks what she intends doing about it and Anna says she's going to win him back. Looking serious, Anna tells Rachel that she'd kill for him and is going to do everything in her power to make sure it works out.
Docks - night
Karen stands against a wall in pain. She rocks her body and struggles against the pain. She notices three men talking together and hides when they split, one heading her way. She follows him, but stops when the witness from the bar calls out to her. It is the man she sat at the table with before leaving with Davies; she pretends not to know him. He tells her that the police are looking for her in connection with Davies' disappearance and she should talk to Detective Royce. Karen takes the card he passes to her, turning to leave she doubles over again in pain. The witness refuses to leave when asked and offers to get whatever she needs, assuming she is a drug addict in need of a fix. Karen agrees and draws him into an alley. There is a scream, followed by a bright light. Karen leaves the alley with a look of satisfaction on her face.
Nick is once again sleeping on the couch. He is moving restlessly, having disturbing dreams about Karen Morgan. He wakes up and is startled to find Anna sitting beside him. Anna apologizes and says she was watching him sleep. She asks him about the nightmare. Nick declines to discuss it and gets up to pull on his denims, telling Anna he has to leave. Anna asks him about their relationship. Nick tells her if he stays things will get complicated and Mike will get hurt just as he's sorting his life out. Anna maintains she and Mike are just friends, but Nick simply tells her to discuss it with Mike and leaves.
Rachel shows Royce images of the blood cells on video. She shows him what happens when blood from the knife is added to regular human cells; the blood cells from the knife spark and attack the normal cells. Rachel concludes that the blood on the knife isn't human.
Anna tells Rachel that the man is playing hard to get. Rachel responds that he may not be as certain about his feelings as her. Anna angrily states that he knows how he feels. Rachel comments that Anna is acting obsessively. She replies that true love is about doing whatever it takes to realize it and when she has his love she will be redeemed. Rachel asks in what way. Anna tells her that everything she has done won't be in vain and the end justifies the means no matter what the sacrifice. Rachel says that depends on how far you have to go to reach the end. Anna tells Rachel that she has been to some dark places and doesn't want to go there again. Once they are together everything will be fine. Rachel looks concerned.
Nick is in the Control Room, looking over some case notes left by Royce when the phone buzzes. The main gate informs him that a woman is there to see him. Nick taps a few keys on the computer and an image of a very wet Anna comes up on a monitor. He tells the gate to let her in.
Later, in Nick's room, Anna changes into dry clothes and apologizes for turning up at the house, adding she had nowhere else to go. Nick notices a bruise on her cheek and asks if Mike did it. Anna tells him Mike got angry when she told him how she felt and he got drunk. Nick comments that he thought Mike could handle the truth, but should have known better. Anna says she tried to get Mike to stop drinking, but he didn't know what he was doing and hit her. She blames herself since she was Mike's support system and he couldn't handle it when she pulled away. Nick states that he should have seen it coming. Anna tries to console him and says she feels guilty because of how she feels about Nick. She tells Nick that everything would okay if they were able to make things work between them. They kiss and fall back on to the bed.
Later, Anna and Nick are in bed together. Anna watches as Nick sleeps, then she gets out of the bed.
Royce wakes up to see Rachel standing over him. She tells him that she had to see him and climbs on to the bed. He doesn't understand what she is doing there. Rachel says he doesn't have to understand or do anything. She leans over and kisses him roughly, as Royce begins to struggle. Ribbons of energy flow from her eyes and mouth; Royce screams in agony. Rachel begins to struggle against her and pulls back, turning back into Karen Morgan. She smashes a window and escapes into the night.
Nick wakes up to see Anna in the bed next to him. Just at that point, Rachel knocks on Nick's door and he shouts that he'll be right there. Anna urges him not to tell Rachel she is there. Nick peaks round the door and Rachel tells him that Royce was attacked last night and is in bad shape. Nick goes back inside and tells Anna to leave whenever she wants. Anna asks if she can see him again later, but Nick tells her it isn't a good idea. Everything is happening too fast and Mike is still his friend. Nick tells her he's sorry but Anna says she understands. Nick kisses her on the cheek and leaves. Anna doesn't look happy.
Rose Mercy State Hospital
Nick informs Rachel that Royce may never regain his eyesight, as they head to his room. Rachel remarks that this wasn’t a coincidence and that Royce must have been getting close to the killer. They enter Royce's room and see him lying down with bandages wrapped around his head, covering his eyes. Rachel moves towards the bed and begins speaking to him, however he reacts violently and demands to know why Rachel did this to him. Rachel, confused, tries to calm him down as the nurse comes in. Royce pleads with the nurse to make Rachel leave.
Rachel asks Nick why Royce was saying those things about her. Nick says he lost a lot of blood, was full of painkillers and his head was probably like 'mush'. Rachel insists that Royce seemed to think she was some kind of monster and wonders if he was attacked by someone who looks like her. Nick teasingly asks if Rachel has a demented twin sister. Rachel wonders if someone or something is going around town changing his/her appearance and attacking victims. Nick, looking suddenly thoughtful, notes that their eyes were messed up. He taps a few keys on the computer and brings up a picture of a man with blackened eyes. Rachel remembers that he was killed by the succubus, Karen Morgan. Nick adds that a succubus can change appearance and asks Rachel where the first attack took place. Rachel tells him it was a bar called the Breakwater Club, near the dock. Nick realizes that the bar is near the pier where they dumped Karen Morgan into the water and tells Rachel she is the one doing the killing. Rachel asks why he is so sure. He tells Rachel that he's seen her and that she is the woman Mike has fallen in love with - Anna. He realizes that Karen is using Mike to get to him. Rachel tells him that she has been working with a patient called Anna who is totally obsessive about love and would kill to obtain it. Nick suddenly realizes that Mike is in danger and rushes out, followed by Rachel.
As Anna walks in, the phone starts ringing but she disconnects it as she doubles over in pain. She calls out for Mike and answers from the basement. Anna goes downstairs and Mike tells her he's looking for candles for their romantic dinner. Anna tells him they don't need candles and he scolds her lack of romance. As Anna is about to make some excuse for not being there, Mike tells her he was going to wait until that evening to ask her to move in with him. Anna doubles over in pain and a concerned Mike asks if she is okay. She turns to leave, but he stops her. Turning away from him, Anna clenches her hand so hard that the fingernails stab into the palm of her hand, drawing blood. Mike assures her that they can work things out. Anna struggles to contain herself, but loses control. She turns around quickly and belts Mike across the face. He's knocked back against the staircase. Anna moves towards him and kisses him hard. Mike struggles, but she drains him of life.
Nick and Rachel arrive at the house to find it dark and empty. Nick tells Rachel that they have to get Mike out before Karen realizes what is going on. Rachel goes to check upstairs, as Nick pulls out his gun and heads down into the basement. Descending the stairs slowly, Nick calls out for Mike, while shining the torch around. He heads towards the closet with the padlock.
Upstairs, Rachel moves around the rooms, searching. As she enters a room, Karen grabs her and throws her against a wall, knocking her out. Karen heads downstairs.
Nick breaks open the closet and pulls aside the tarpaulin to find Mike's body with blackened eyes. Stunned, Nick backs away, but Karen is behind him. Nick aims the gun, but she is too fast and knocks it out of his hand. She pushes him up against the wall. Nick angrily tells her that Mike wasn't a threat to her, but Karen argues that he was a threat to their happiness. She shakes her head and the blonde hair disappears to be replaced by dark hair. She asks Nick if he thinks she enjoys killing to sustain her life. She wants to be normal and to love someone like him, convinced his love in turn will help her change. Disgusted, Nick tells her he doesn't love her. She argues that he proved it last night when they slept together. Nick tells her it was an illusion and that nothing between them was ever real. Karen gets angry and tells him she thought he was special but he's just like all the rest. Nick attacks her, but she grabs him around the throat, telling him she didn't want this. She opens her mouth and the energy ribbons begin to flow, but before she can make contact, she violently jerks back. She lets go of Nick and he falls to the side. Rachel stands behind them, aiming a gun at Karen. She fires three more times and Karen falls backwards into the closet. Nick rushes over, slams the door shut and locks it again. He tells Rachel to get matches, as he pours gasoline over the door. Karen pleads with him, but Nick lights the match and sets the door alight. Karen screams, as she is consumed by fire.
Rose Mercy State Hospital
Rachel explains to Royce about Karen and he says he doesn't understand why Karen chose to look like Rachel. Embarrassed, Rachel explains that a succubus appears in the form of someone the victim desires. This time Royce is the one who gets embarrassed, as Rachel leaves to find Nick.
Outside, Nick is leaning morosely against his car, deep in thought:
"I tried to imagine carrying a hunger like hers, to want love so badly only never to taste it. It's a tortured existence and on the deepest level I think she knew. I told her that everything between us was an illusion, I wonder now if I was speaking the truth."