Colin Firth has joined the cast of 'Before I Go To Sleep'.

The 'Love Actually' star will play Nicole Kidman's secretive husband in the big screen adaptation of British author S.J. Watson's bestseller about a woman with amnesia who wakes up every morning with no knowledge of her identity, only to be reassured daily by the man who claims to be her long-term partner.

To help rebuild her life, she keeps a journal and relies heavily on her husband. But when she receives a phone call from a worried doctor warning her to be more careful, she realises everything is not as it seems.

'Brighton Rock's Rowan Joffe has scripted the thriller and is also on board to direct while Liza Marshall, Ridley Scott and Mark Gill are producing, Variety reports.

'Zero Dark Thirty' actor Mark Strong and Anne-Marie Duff will round out the cast.

Colin, 52, and Nicole, 45, have just wrapped filming on World War II drama 'The Railway Man', in which they also played a man and wife. The film sees Colin take on the role of a former Japanese prisoner of war, who reconciles with one of his captors 30 years later. 'War Horse' breakout star Jeremy Irvine is also attached as a young version of Colin's character.

Filming for 'Before I Go To Sleep' begins at London's Twickenham Studios at the end of February.