France, 1915: Lieutenant Tom Donald envies everything about fellow officer Frank Foden - his confidence, his easy manner with the men in the trenches, the affectionate letters from his wife. Frank shares these letters happily, drawing Tom into a vicarious friendship with a woman he's never met. Although the bonds of friendship forged under fire are strong, Tom can't be so open with Frank - he's attracted to men and could never confess that to anyone.

When Frank is killed in no-man's-land, he leaves behind a mysterious request for Tom: to deliver a sealed letter to a man named Palmer. Tom undertakes the commission while on leave - and discovers that almost everything he thought he knew about Frank is a lie....