See the play if you can (spoiler)

Didn't realise when I rented the movie, but I'd seen the play on which it was based some years ago, called Point of Death. The play is set solely in the hospital ward, and is much clearer in its explanation. Simon wakes up in hospital after an accident with a loss of memory, he then experiences a series of nightmarish hallucinations (which were very cleverly presented), as a result of which he remembers/admits to killing someone previously (not as a result of the crash). It is then revealed that he had died in the crash, but was unable to pass over until he admitted his guilt.