Asylum (2005)

There's a dark and sinister triangle of intrigue in this unusual thriller. Natasha Richardson plays Stella, an attractive woman who's married to a very dull, boring psychologist. He works in a maximum-security psychiatric hospital, and his wife is so bored that she embarks on a risky and dangerous affair with Edgar, a handsome inmate - not realising that he is completely and violently insane. Unbeknown to Stella, her affair is being manipulated by the slimy, ambitious and deeply unpleasant Dr Cleave, played by the excellent Ian McKellen. All forming part of his dastardly plan, Dr Cleave is unaware that in plotting Stella's downfall he is involving himself in a sinister and dangerous situation that's potentially very explosive...