Wee Angus lives as a servant's son in a large manor house alongside a Scottish loch. One day he discovers a mysterious egg and takes it home, where it hatchs and grows and grows, acquires the name Crusoe and becomes Angus's best mate. Being WW2 the 12th Medium Regiment Royal Artillery are camped nearby to keep the loch secure, but they wouldn't know a Kelpie, a supernatural shape-shifting water horse, from a U-boat, putting Crusoe in a wee bit of danger. But being a family film don't worry be happy, Crusoe's going to escape the beastly military and make it with one fine jump over that anti-submarine net to the wide open sea. Excellent.