It is 1915. Jim Linton and Wally Meadows, half a world away from Australia and Billabong, are serving in the British Army. During their initiation into the horrors of trench warfare in France, they experience the enemy's deadly new weapon: poison gas. They both spend their convalescence in the green countryside of Ireland, together with Jim's sixteen-year-old sister, Norah, and their father, David. But the rest days spent fishing and riding across the hills, bring unexpected and perilous drama, which they share with a new friend, the gallant Irishman, John O'Neill.