In the library at St. Athanasius, an exclusive Catholic school, Joseph Dawkins is being harassed by bully Brad Rollins, and dreams of revenge. In a remote area of the stacks, Joseph discovers something that could provide it: a journal of a member of the "Legerdemain Club," an organization banned at the school in 1966 after strange things occurred. Within the diary he finds instructions for a performing a ritual for summoning "The Warden," who promises power to the powerless, and with his two friends George and Arthur he breaks into a pathology lab that night to use a dead man's hand as the "Hand of Glory" in the ritual. It appears to work, as the disembodied hand stands upright and the fingers burst into flames. George and Arthur run away in fright, but Joseph stays, staring in fascination at the burning Hand.
At the Legacy house, Philip and Derek are discussing Philip's decision to leave the Legacy and go back to his parish. Derek convinces him to take on one last task: Philip's old friend Monsignor Grey has asked for his help in locating a missing faculty member. Nick goes along to help.
Joseph and his friends are surprised and alarmed when their chemistry teacher, Mr. Klein, goes missing and a mysterious substitute shows up. This is Samuel Warden, who makes it clear that he is the one they summoned. He is reviving the Legerdemain Club, and attendance for the three boys is "mandatory." He demonstrates his powers of magic by summoning a swarm of insects -- that no one else can see -- to attack Brad.
Philip is introduced to Warden, and recognizes him for what he is: immensely old, and totally evil. And he knows that Warden realizes that he knows.
The leader of the Legerdemain Club in 1966 was named Andrews; and Warden now lives at his seemingly) abandoned house. One room, however, is magically preserved, and the three boys are summoned there. Warden gives them their "scripts" for the school program the following night, and reveals that Andrews did not hang himself but was in fact poisoned. When they leave wediscover that Warden is keeping the missing teacher, Klein, a prisoner in the dark basement.
After performing a healing for Brad at the hospital, Philip along with Nick returns to the school to examine the records and discovers more information about Andrews. Philip then talks with the boys, telling them that he knows about the Club and the Warden; and warning them of the danger tells them that he is the only person who can help them. They are too frightened to talk with him--except for Joseph, who asks him to come that night to his house.
At the Legacy House, Derek, Alex and Rachel are investigating Warden as well. Until he showed up at the school, he did not seem to exist. Derek discovers that "S. Warden" is an anagram of "Andrews;" they are the same being.
Warden launches a magical attack on Nick and Philip as they are on their way to see Joseph. He seizes control of the car through Nick; only by splashing holy water on him does Philip break this control. While it was Nick who was splashed, it is Warden whose face is burned.
At Joseph's house, the boy reveals the diary and confesses to performing the ritual with the Hand of Glory; he and his friends are now Warden's prisoners. He also reveals that the Legerdemain Club will be performing that night at the school program.
Hurrying to Andrews' house in an effort to find the missing Klein--as records had revealed that it was he who was most instrumental in defeating Andrews 30 years before--they discover he had been there but was now gone. Fearing Warden's plans, they hurry back to the school--with a detour by Joseph's locker to get the Hand of Glory.
Warden's plans are to use Klein as a human sacrifice to gain revenge on the people of the community. Just as it seems his power is too great to fight, Philip bursts in, carrying the burning Hand of Glory. He chants his own ritual (below) to send the Warden back to Hell in flames, thus saving everyone's lives.