Atonement. The 2007 film directed by Joe Wright and starring James McAvoy and Keira Knightley. From Ian McEwan’s 2001 novel of the same name.
Cecelia (Knightley) is the elder of the two wealthy Tallis sisters, her younger sister is 13 year old Briony (Saoirse Ronan). Robbie (McAvoy) is the housekeepers son who has a Cambridge education courtesy of his mother's employer.
Briony witnesses sexual tension between Cecelia and Robbie and misunderstands what she sees. She blames Robbie for something he didn’t do. With far reaching consequences.
Keira Knightley gives an unusually natural performance and James McAvoy is as solid and believable as ever. Vanessa Redgraves’ performance in the final act is superb.
Not entirely unexpectedly, the film is about regret. It’s 2 hours worth of totally engrossing drama with a great ending, a really great ending. Highly recommended.