This powerful and highly disturbing psychological thriller, directed by David Cronenberg and starring Jeremy Irons and Geneviève Bujold, works extremely well. It doesn't need too many special effects; the premise - of twin gynaecologist brothers, one whom is successful with women and passes them over to his brother when he's bored with them - is disturbing enough, but then, when the shy brother falls in love, it gets seriously out of hand as they begin a terrifying descent into drugs and madness.
If that wasn't enough, Irons produces a powerhouse performance, playing both the twins Beverly and Elliot Mantle. Add in Bujold as the famous and infertile actress who's torn between the two brothers, and you've got a belter of a movie.