After a mass murder at an Internet security company, evidence indicates that the person responsible is not a typical serial killer; Prentiss is required to complete recertification training.
Kate's original crime is revealed; Locke and Eko discover something interesting about the film; Michael has a mysterious encounter with a computer.
Led by Rousseau to a mysterious captive in the jungle, Sayid becomes determined to find out whether the man is one of the "Others."
Sark kidnaps Neil Caplan a Cal Tech mathmetician along with his wife and child.
While investigating a rural religious cult, the agents expose a sinister experiment involving violent teens and alien DNA.