Seventeen year-old Daphne Janus is floored when her parents agree to let her accompany her best friend to a getaway resort on an island off the coast of California. She doesn't know her parents have sent her to the Purgatorium as a last-ditch effort to save their child. Her best friend and life-long neighbor takes her to a mostly uninhabited island with a wildlife preserve on one side and Chumash Indian ruins on the “haunted” side. The resort might be beautiful, the beach pristine, and the views from the headland amazing, but strange things begin to happen that soon have Daphne running for her life. At first she finds the therapeutic games thrilling: the ghosts that visit her room, the dropping elevator, and the kayak incident are actually kind of fun once she recovers from them. But when her horse bucks her off during a trail ride and she becomes lost on the haunted side of the island, it’s not fun anymore, and she wonders if her parents have sent her there to help her or to punish her.

After enduring Dr. Hortense Gray’s experimental therapy on an island off the coast of California at a compound known as The Purgatorium, seventeen-year-old Daphne is delighted to learn she will now have a chance to have revenge on her parents and boyfriend by participating in their therapy. It’s payback time, and Daphne can’t wait to begin. Dr. Gray defends her dubious methods by claiming that all treatments come with risks, but when real bullets fly and lives are at stake, Daphne decides she wants no part of it and hatches a plan to save her family.

Daphne returns to the island to save her best friend, Cam, and the other "Calibans" who've been brainwashed by Dr. Gray, but, once again, things aren't what they seem. Daphne's entire world comes crashing down along with the Purgatorium when federal ATF officers arrive with a warrant during a dangerous exercise. What she believed to be so isn't, and the blurry line between art and reality leaves her reeling.