Patients and staff are being systematically slaughtered at Greystone.  After three murders in just two weeks leave local police stumped, they turn to the New Jersey State Police for help.  You, a detective with the state police, enter Greystone undercover as a patient.  Since everyone in Greystone is a suspect nobody on Greystone's staff knows your true identity.  As far as everyone is concerned, you're just another patient with problems.

Exploring Greystone will be challenging as there are acres of land to be explored. You have to make your way through underground tunnel systems and a dozen or so buildings, both active and abandoned, and even the surrounding neighborhood in search of clues, evidence and witnesses as you pursue the killer.