The Price of Things (1930)

Courtenay John Dayre is drugged by a jealous spy on the night before his loveless marriage to Anthea. His twin, John Courtenay Dayre, reluctantly agrees to impersonate his brother at the wedding, only to discover a genuine affection for his accidental wife. Meanwhile, Courtenay begins to understand the price of things when he realises that his affair has allowed a valuable military secret to be stolen.