In the opening credits scene reminiscent of 'Maniac', a man is shown putting on a policeman's uniform with a badge, gun belt, and cap. That same night, a young woman, named Cassie Phillips (Jill Gatsby), leaves a local bar at night where she is attacked by two punks on the street who try to rob her. She runs and hides, then calls out to a police officer she sees in a nearby park square and runs up to him. She gasps when she sees his face and as the two punks watch from a distance, the policeman picks her up with his white-gloved hands and kills her by breaking her neck. The next day, the two punks are arrested where they tell the police that a cop was responsible. Detectives Frank McCrae (Tom Atkins) and Lovejoy (Lou Bonacki) see the woman's body at the morgue and Frank believes the punks claim of a murderous policeman.The following night, a man and a woman are driving through Manhattan late when they stop at a red traffic light. A cop approaches the car on foot and taps on the driver's side window with a billy club. The unseen cop takes the man to the front of the car for a sobriety test and the woman watches as the unseen cop takes a large blade out of the billy club and swipes twice and throws the dead man on the windshield of the car, splattering blood all over the windshield. The woman screams, gets in the driver's seat and speeds away, turing on the wiper blades to wash the blood off the windshield.The next morning, Frank goes to see the police Commissioner Pike (Richard Roundtree) at his office and suggests giving policemen mental tests due to this latest killing. Pike refuses and tells Frank to keep quiet about the killings and makes a veiled threat by bringing up that Frank tried to shoot himself in an attempted suicide several years ago after his partner was killed in the line of duty.That same evening, a man walking alone on a street has an encounter with the unseen killer cop who throws him against a car and handcuffs him. The man runs when the unseen cop pulls out his blade from his billy club. The cop catches up and shoves the man forward who trips and falls into the sidewalk pavement that is wet cement. The unseen cop puts his blade away and instead suffocates the man by shoving his face into the cement. The next day, work crews are forced to jackhammer the victim out of the dried cement.After a morning news story of a so-called "maniac cop" responsible for the three recent murders runs, people all over New York are in a panic. In a warehouse section of Queens, a woman has car trouble when a policeman pulls up behind her and gets out. When the policeman knocks on her window, the fearful woman pulls out a gun and shoots and kills the policeman... who is not the maniac cop.Meanwhile, Jack Forrest (Bruce Campbell) is putting on his NYPD uniform and he and his wife Ellen (Victora Catlin) argue about his job that he spends more time on the street then home. She says that she's afraid that he might hurt her in his sleep. After Jack leaves, Ellen gets a phone call from an unseen woman who has called her before and tells Ellen that Jack is the maniac cop and that he will kill again. Ellen gets a gun and follows Jack to a local motel somewhere in Manhattan. After talking to the manager (director William Lustig) who tells her that Jack has been there before, she goes to the room where Jack is and catches him in bed with another woman. Ellen points the gun at Jack and the woman without letting Jack explain. Angry over his infidelity, but relived that he is not the maniac cop, Ellen leaves. As she goes to her car, she is grabbed by the real maniac cop and pulled into a van which drives away.The next morning, a maid at the motel finds Ellen dead in the same room that Jack has rented hours earlier. The hot-headed Captain Ripley (William Smith), Jack's superior, arrives at Jack's house to inform him about his wife's murder and when Jack admits to being at the motel the previous night, Ripley arrests him for the murder. In an interrogation room, Ripley and Frank show Jack a collection of "Maniac Cop" news articles (belonging to Ellen), and read a page from Ellen's diary saying that she thinks Jack is the killer. Jack continues to deny that he is the Maniac Cop but refuses to answer any more questions. Jack's lawyer arrives minutes later where Jack tells him that he has a witness who was with him around the time Ellen was murdered, but he would like to keep her out of it. Frank tells Captain Ripley that he believes that Jack is not the Maniac Cop, but he also believes that Jack is protecting someone. But the slimeball Ripley refuses to accept this and tells Frank that he plots to charge Jack with all of the killings. Frank goes to visit Jack in his cell where he finally admits that he was with Theresa Mallory.Meanwhile, Theresa Mallory (Laurene Landon) is revealed to be a vice cop and is seen posing as a prostitute when she is attacked by the Maniac Cop. Frank arrives and they both open fire on the Maniac Cop who flees. They go to a local bar for drinks to talk about Jack's situation and Theresa says that the only person she told about her and Jack was Sally Noland (Sheree North), a middle-aged crippled policewoman who works in the clerical room at the precinct. Frank goes to see Sally (who walks with a cane and a leg brace) where he tells her about Theresa being attacked.Later, Frank follows Theresa in his car to a local pier on the Hudson River where she watches her talk to the stout, but still unseen Maniac Cop. Sally tells the killer cop about Jack's arrest and that if he relaxes with the killing spree, Jack will be blamed for all the killings and once they let their guard down, he can go after the commissioner, the mayor and everyone else responsible for his false incarceration. Sally calls the Maniac Cop "Matt" and tells him to save his murderous rampage for the people who only did wrong to him. She spots Frank spying on them and opens fire, forcing Frank to run to his car and drive away.Frank goes to see Clancy (James Dixon) in the records department and reads old newspaper articles about a policeman named Matt Cordell (Robert Z'Dar), who was thrown into Sing Sing prison for "violation of people's rights". Clancy tells Frank that Matt Cordell has been dead for over 10 years and that his girlfriend, who was Sally Noland, attempted to commit suicide by jumping out of a window after his imprisonment, but was only crippled with a fractured left leg. Clancy tells Frank that Cordell was a well known and respected cop, but had little regard for the rules of the force. Cordell claimed during his trial that his own superiors plotted to frame him and send him to prison after seeing that he was a trouble maker on the force, but his conviction put the complaint at moot.Meanwhile, the Maniac Cop, Cordell relaxes at his warehouse hideout where he thinks back to being sentenced to several years in prison by a judge and arrives in Sing Sing where he is recognized by all of the inmates that he arrested and put there. In the showers, Cordell is attacked by three knife-wielding inmates. Cordell puts up a fight and beats up the three men until one of them stabs him in the back. He falls and the rest of the men stab and slash him in the face over and over again.Frank and Theresa go to see Jack in jail where they tell him about their suspicions that Matt Cordell, who may have died in prison as was detailed in the news 10 years ago, may be committing the murders. Theresa and Jack are left alone to kiss, while Frank goes to the clerical room where he is beaten by Sally with her cane and says "He knows I'm no good to him anymore!" She leaves and suddenly sees a dead cop and screams: "He's here!" The still unseen Cordell appears and grabs Sally and Frank attempts to lead her away. Cordell slams Sally against a wall with clearly superhuman strength. Frank pulls out his gun, but is thrown across the room by the Maniac Cop.During this, Theresa sees a dead cops outside of the cell blocks and knows the Maniac Cop is there at the station. She lets Jack out of his cell where he takes a gun off a dead policeman and tells Theresa to wait in Frank's car. When Theresa goes outside, Frank is thrown by Cordell through a window and lands on a parked taxi next to Theresa. Back in the station, Detective Lovejoy arrives and points a gun at Jack, thinking that he is killing everyone. He goes for a phone and reacts to touching Sally's dead fingers. Jack punches him out, gets his gun and runs outside where he meet Theresa and they drive away.The next morning, Jack and Theresa go to visit Dr. Gruber at Sing Sing's infirmary (Jack tells him that he is Frank McCrae and that he has an appointment). After preliminary questions, Gruber finally admits that, on the day that Cordell was attacked in the showers, the doctor discovered that he was still alive, and revived the near-death officer. Despite being stabbed multiple times, Cordell was technically brain dead, yet he continued to live. Sympathetic to Cordell's plight and aware that Cordell was framed by his own superiors, Gruber declared Cordell legally dead and did not see any harm in making people think he was still alive (which he was technically not).That same day, the St. Patrick's Day parade is being held. While Jack waits outside in Frank's car, Theresa goes to police headquarters to warn Commissioner Pike that Cordell will be coming after him. Theresa makes her way to the commissioner's office where she tells him who she thinks the real Maniac Cop is, but Pike and Ripley believe that Theresa aided in Jack's escape and refuse to believe her. (It is implied that both Commissioner Pike and Captain Ripley were part of the conspiracy to frame Cordell for trumped-up criminal charges to get rid of him). A policeman arrives to arrest Theresa while Pike and Ripley leave and they are both murdered by Cordell in an elevator. The cop handcuffs Theresa to him and as they are walking down a hallway, Cordell appears and stabs him in the stomach with his billyclub blade. Theresa gets to a room where she managed to uncuff herself and climbs out onto a ledge as Jack watches. Just then, a group of policemen, whom still think that Jack is responsible for all the killings, see him and throw him into a police van.The still-unseen Matt Cordell pulls the driver out of the police van and drives away with Jack. Theresa gets in cop car with another officer and they follow them to Pier 14, which is Cordell's hideout. Cordell stops the vehicle in his warehouse hideout and he starts to axe the door open. When Jack attempts to break out, Cordell (who's horribly scarred and decomposing disfigured face is finally seen) picks Jack up and throws him on Theresa who arrives and approaches with a shotgun. Cordell picks up the shotgun and blows away the other cop as he runs in. Jack knocks the gun away from the maniac cop, and he is punched by the super strong undead Cordell. When police sirens are heard, Cordell gets back into the police van and attempts to drive away. Jack jumps on and attempts to stop him from escaping. While driving erratically on the pier, the van runs into a suspended tube that crashes through the windshield and pierces Cordell's chest. The truck, Cordell and Jack fly off the end of the dock and crash into the water.A little later, while Jack and Theresa watch, the paddy wagon is pulled from the water by a police salvage team, but Cordell is not inside. Unseen down in the water a short distance away, Cordell's hand comes out...
Output: Question: Who was hiding behind a curtain?, Answer: Cordell