Attending a reunion, two Australian ex-servicemen reminisce about their exploits in France during WW1. These include lying in a field hospital where they feigned deafness to extend their recuperation, stealing jars of rum from the Quartermaster and inventing an elaborate ruse to hide them and finally, the night before returning to the front relaxing in a French café where romance blossoms between the soldier and waitress as told through the song 'Mademoiselle from Armentieres'.

Chic Williams (Pat Hanna) and his friend James Brown (Norman French) elude a private detective who's been following them, and head off to the bush (only later is it revealed that the detective wants to tell James he's inherited a fortune).

The diggers and their officer, who has fallen for a nurse at the hospital, are subtly manipulated by a British intelligence officer to assist in passing false battle plans to the Germans. Given leave in England, they end up billeted at a country house and offered barley water instead of the home-brew they anticipated.