AustLit

 'On Billabong station Jim, now assistant to his father, breaks in a promising young colt, and with Norah and Wally, helps with the intricacies of hauling a large bullock from the depths of a mud hole.  World War I is underway.  Jim and Wally want to enlist.  Mr. Linton needs to travel to London on family business so they all set sail on the Perseus, a huge ocean liner carrying produce to Europe, to involve themselves in the war effort.  On board they observe black-out restrictions to avoid being detected at night by enemy destroyers and deal physically with a German spy.  They have an all too interesting time during their stopover in Durban, South Africa.  Then their ship is captured by an enemy warship and almost sunk before a dramatic rescue takes place, allowing them to eventually reach London safely where the boys enlist in the British Army. '  (Publication summary)