Shallow Grave (1994)

To avoid spoiling the movie this plot summary is very brief. It starts when three people living together in a four bedroom flat are looking for a house mate. The interviews they conduct are very unorthodox and very funny. Eventually the three agree on one prospective tenant. He moves in, locks his door, and is not seen again. After a couple of days the three become curious and break in to his room. What follows is an amazing piece of cinema and to say more would ruin it.