The film opens with television producer Jerry Hartfield describing Grave Encounters, a paranormal reality television program directed by and starring ghost hunter Lance Preston, which was canceled after five episodes. Hartfield explains that the events about to be shown in the film is raw footage from the sixth and final episode filmed, edited only for time-restraint purposes.The footage shows the crew of Grave Encounters composed of Lance himself, occult specialist Sasha Parker, technical expert Matt White, cameraman T. C. Gibson, and guest starring psychic medium Houston Greypreparing to investigate the abandoned Collingwood Psychiatric Hospital where unexplained phenomena has been reported for years. They receive a tour of Collingwood and its underground tunnels from the hospital's caretaker. They also learn about Collingwood's history, including a physician named Arthur Friedkin, who performed unethical experiments and lobotomies on the patients at the hospital before being killed by escaped patients. The crew voluntarily lock themselves inside Collingwood for the night and begin their investigation, setting up camp near the hospital's main entrance, which is locked from the outside. No paranormal activity occurs for the first few hours until a door slams behind T. C. by itself while he is filming around the building. Lance and his crew try to establish contact with the unseen entities responsible, and are further tormented by more hauntings, which become increasingly blatant and hostile.With half an hour left before the hospital caretaker comes to unlock the front doors, the crew starts packing. Matt goes to retrieve the cameras stationed throughout the building, but disappears. The others spend the next several hours looking for Matt without success, with the caretaker not arriving. They knock down the front doors to escape, only to discover it leads to another corridor, as do several other "exit" doors they find. They also notice that it is still night outside when it should be daylight. The crew continues searching for both Matt and an exit when they encounter a girl whose face contorts demonically. The crew flees in fear, but Houston is separated from the others and later violently assaulted by an unseen force, killing him. While resting, the others find hospital tags bearing their names on their wrists. They eventually find Matt, who is wearing a hospital gown and has been driven insane, mumbling nonsense about his apparent psychological disorder, and explaining that the only way for them to escape is for them to "get better" at the hands of the hospital's unseen residents.The crew continues to be chased through the hospital by several apparitions. T. C. is pulled into a bathtub filled with blood by a ghost and disappears, while Matt falls down an elevator shaft to his death as Lance and Sasha are attacked by a tongueless demon. Lance and Sasha enter the tunnels in search of another exit where Sasha, who has become violently ill, disappears in a mist that appears while she and Lance sleep. Terrified and insane, Lance continues through the tunnels alone, surviving by killing and eating rats, until he finds a door leading to Friedkin's operating room that contains an altar and pentagram for a demonic ritual, showing that Friedkin had used black magic for medical practice. He turns to see the apparitions of Friedkin and several nurses, who drag a screaming Lance onto their operating table. The camera blanks out for a moment before showing a lobotomized Lance, who says he is now "better" and allowed to go home, and gives a few parting words to the audience before the screen cuts to blue.