This slick, occasionally disturbing German thriller (adapted from Mario Giordano's novel Black Box ) was inspired directly by the notorious Stanford University prison psychology studies of the early '70s. Filmically, it borrows from Shock Corridor in sending undercover a journalist, Tarek Fahd (Bleibtreu) as an inmate participating in a university-administered exploration of prisoner-guard relations, where volunteers adopt roles in a lab environment of punishment and humiliation. What starts as a challenging investigative model soon slides out of control as peer pressure, dehumanisation and sadism threaten the lives of the participants. Given extra resonance by Germany's history, the film works effectively enough both as a psycho-social critique of the limits of behavioural safeguards and in the suspense stakes. The tension is grounded in character relations and their shifts under pressure as much as in the cranking of the narrative. By the climax, this develops into a standard shoot-out and clean-up operation, but there still remains a disquieting sense of the film-makers' initial intentions.