11. Lethe

Complete story — includes the ending

Reese leaves the team and heads for Colorado, where his father had lived. The Machine provides a new number to Harold, who at first is reluctant, but eventually accepts it on Root's insistence. The number belongs to Arthur Claypool ( Saul Rubinek ), Harold's close friend during his days at MIT. Claypool has been diagnosed with a brain tumor and is being monitored at the hospital, being kept under Secret Service guard. Arthur's wife, Diane ( Camryn Manheim ) tells the disguised Doctor Shaw that Arthur works for the NSA, and Collier's group Vigilance tries to abduct him. They escape to a hotel, where Harold talks to Arthur to get more information about Samaritan: a project which sought to build an AI, like the later Machine, but was shut down just as it achieved consciousness. As Arthur talks with Finch, he remembers that his wife is dead, prompting the woman pretending to be Diane to reveal herself as Control. She threatens to kill either Arthur or Harold unless one of them gives up their respective AI. The Machine starts analyzing threats to its assets and itself, changing Samaritan's status from "Deactivated" to "Unknown".