On the eve of his retirement, ailing London barrister Sir Wilfred Robarts (Laughton) elects to defend one Leonard Vole (Tyrone Power), an amiable young man accused of murdering a rich, elderly widow he'd befriended. So the normally unflappable Robarts is mystified when Vole's German wife Christine (Dietrich) announces she'll testify against him. 

Adapted from Agatha Christie's celebrated stage play, Wilder's quintessential 1957 courtroom drama steadily builds narrative tension with its crisp, cynical dialogue. Surprises of identity, double and triple crosses, and a succession of plot twists keep this "Witness" from becoming predictable. Laughton and real-life wife Elsa Lanchester, playing Robarts's meddlesome nurse, both won Oscars for their roles, but it's Wilder's razor-sharp script and direction that make this mystery tick. Sadly, this was Power's last completed role.