a boy named Angus MacMorrow lives in the large manor house of Lord Killin on the shores of Loch Ness with his mother Anne MacMorrow (the housekeeper),
One day, while collecting seashells, he discovers what appears to be a large mysterious egg in the sand, which he leaves it in his father's shed. When he returns later, an unknown creature hatches (which he calls 'Crusoe' after Robinson Crusoe) that becomes the fabled Loch Ness Monster. Angus keeps the creature a secret, but eventually tells his sister and (reluctantly) Lewis about it. Lewis explains to Angus that it is a genderless "Water Horse" that lays one egg, then dies before it hatches.