“I couldn't have done it . . . could I?” In a twist on the wrong-man theme, this hybrid of playful murder mystery and psychological melodrama stars John Mills as an innocent man whose own self-doubt makes him a suspect. After a bus accident kills a child in his care and leaves him with a fractured skull and troubled mind, Mills seeks refuge in a small hotel whose very proper residents greet him with a mixture of curiosity and condescension. When an attractive lodger goes out to post a letter and doesn't return, the neighbors, the police, and Mills himself all begin to wonder whether he might be responsible. Erwin Hillier's cinematography shrouds the action in an atmosphere of misty, pervasive melancholia, and Mills brings an otherworldly, fretful presence to Eric Ambler's alternately sardonic and empathetic scenario, which hints at the struggles of men shattered not by accident but by the recent war.