Chartered accountant David Stephens shares a flat in Edinburgh with physician Juliet Miller and journalist Alex Law. Needing a new flatmate, the trio interview several applicants in a calculatedly cruel manner, amusing themselves at the applicants' expense before finally offering the room to a mysterious man named Hugo. Shortly after he moves in the trio finds Hugo dead from an apparent drug overdose in his room, as well as a large suitcase full of money. They agree to conceal the death and keep the money for themselves. They decided to remove the identifying features--hands, feet, and teeth--from Hugo's body and bury the remains in the woods. David is given the gruesome task of dismembering the corpse after they draw lots, while Juliet disposes of the leftovers in her hospital's incinerator. Unknown to them, Hugo is being sought by a pair of violent criminals who are torturing and murdering informants as they follow Hugo's trail. The flat below theirs is broken into, making them anxious. The police, investigating the intrusion, are surprised when the three friends deny that they ever had a fourth flatmate. While Juliet and Alex go on a shopping spree with the money to "feel better", David's fears turn into full-blown paranoia. He hides the suitcase of money in the attic and begins living there, drilling holes in the attic floor to watch the living space below. The relationship between the three begins to deteriorate. The criminals break into the flat, coercing Alex and Juliet to reveal where the money is. As the men enter the dark attic, David kills both of them with a hammer and returns to the woods to dispose of the bodies. Alex and Juliet become worried about David's mental state, and David becomes worried that the two are conspiring against him. The bodies are discovered in the woods, and Alex is sent by his editor to cover the story. With the police now closing in, Juliet seduces David into giving her the money so she can buy plane tickets to Rio de Janeiro and they can run away together, but secretly she plans to go alone and leave the other two to take the fall. Alex returns from work and--realising that Juliet and David are working together and that his life is in danger--tries to phone the police, but is stopped by David and Juliet. The confrontation escalates to violence. David reveals that he knew about Juliet's secret plan to betray both him and Alex, and punches her, prompting Alex to attack him too. Alex collapses after being stabbed in the shoulder by David, but Juliet kills David before he can finish the job. With David dead, Juliet decides to force the knife deeper into Alex's shoulder, pinning him to the floor, so that the police will find him with David's body and blame him for all four of the deaths. She flees with the suitcase to the airport--but in the parking lot she breaks down hysterically when she discovers that it is actually filled with hundreds of newspaper clippings about the triple shallow grave, taken from Alex's newspaper. With no possessions other than the plane ticket, and no other way out, she calmly boards the plane to Rio. The police arrive at the flat to find Alex alive and grinning--he had hidden the cash under the same floorboards where Juliet had skewered him. David finishes the monologue that began the film, the entirety of which is now revealed to be a flashback. A sheet is drawn over his face and his body is slid into a drawer in the morgue.—zubair666_