Tilda Swinton has joined the cast of Roman Polanski's political thriller "The Ghost" reports Variety.

An adaptation of the Robert Harris book, the story follows a ghostwriter (Nicolas Cage) hired abruptly to finish the memoirs of an ex-British prime minister (Pierce Brosnan) after the first scribe turned up dead.

The ghostwriter's research leads him to uncover skeletons in the politician's closet that put the writer's life in danger.

Swinton will play the wife of the former prime minister (Brosnan). Her marriage is crumbling, and she falls for the writer. Shooting begins this September in Europe.