Shutter Island is based on the novel of the same name by author Dennis Lehane, who is best known for his Boston area mystery/dramas, Mystic River and Gone Baby Gone. Unlike those other two books, however, Shutter Island is psychological drama that is far deeper and more complex. The challenge facing screenwriter Laeta Kalogridis was how to take all the psychological components of the story and balance them with the pulp mystery narrative that most viewers are expecting.
The actors in the film faced the same challenges. DiCaprio, Kingsley and Ruffalo in particular had a tough time of it. The nature of the story required each of the principal actors to turn in a multi-layered performance of a depth they probably weren’t expecting until they actually got on set and started filming.