Law & Order: Criminal Intent: Season 4, Episode 6

4 - 6: In the Dark

When the body of several murdered homeless men are found sold to medical labs, Detectives Goren and Eames descend into abandoned subway tunnels - where they encounter its tormented inhabitants - until they discover all of the victims were newly registered for credit cards that were maxed out after their deaths. As they probe further, the investigators find a link to a suspicious auto parts salesman and his addled middle-aged girlfriend.