Cordelia ia a troubled, damaged soul who is only just recovering after some unnamed trauma; she is an actor rehearsing a play and comes to stay in a creepy London mansion flat occupied by her twin sister Caroline and Caroline’s boyfriend Matt. When they leave her alone there Cordelia strikes up a friendship with Frank the charming, but strange and unreliable young man they can hear practising his cello in the upstairs flat – a relationship which quickly becomes very disturbing.

He was once a pop star with adoring fans, now even his wife's left him for another woman. So he's kidnapped them both and is driving out of London with a tub full of poison and what he claims is enough antidote for two people. He's going to poison all three of them, then they'll jointly decide who gets to be saved.