Related are the happenings during the fight of Passchendaele while the First Worldwar.
The Canadian officer Michael Dunne is in the centre of the film and its action.
Dunne went back to Canada because he was hurt during the war. Back home he started a relationship with the nurse Sarah.
Her brother David decided to be a soldier and went into the war. Thats the reason why Dunne also decided to go back because he wanted to protect David. Dunne thought he had to do that because of the love to Sarah.