In 1940 England, aristocratic Prudence Cathaway alarms her snobbish parents by joining the WAF service branch. She soon meets and falls in love with the brooding Clive Briggs, despite his prejudice against the upper classes, and agrees to spend a week with him at a Dover hotel. When Clive's soldier friend, Monty, arrives to retrieve him, Prudence learns that Clive went AWOL after Dunkirk, and urges him to recall why England must fight the war.

In 1915 France, Major Brand commands the 39th Squadron of the Royal Flying Corps. The young airmen go up in bullet-riddled "crates" and the casualty rate is appalling, but Brand can't make the "brass hats" at headquarters see reason. Insubordinate air ace Captain Courtney is another thorn in Brand's side...but finds the smile wiped from his face when he rises to command the squadron himself. Everyone keeps a stiff upper lip.