The evil spider, Empress Ravanola plans to steal the Great Ruby of Carminel from the young mouse king and overthrow the Mouse Kingdom with the help of the wicked stoat, Lord Malatesta. But Captain Roamer, a fearless sea-mouse who leads his brave band of buccaneers and the feisty tamarim princess Tamina, defends Carminel and its inhabitants. After a mighty sea battle, the evil lord captures Tamina. Escaping sacrifice to Ravanola's Snake-god, she is brilliantly rescued by Roamer who captures the ruby and kills the Black Widow in the process. The empress defeated, Malatesta gains power and prepares to lead his army to Carminel to destroy the Mouse Kingdom once and for all. But time has passed and the young king is now fully grown. He leads his friends courageously into battle and after a bitter final fight on the ground and in the skies, the mice are victorious. However, as returning troops celebrate, the king is wounded by his evil uncle the Red Duke, and only escapes death by calling upon the special healing power of the ruby.