Horace and Gregory set out to the fall festival as is the custom in their island kingdom. As part of the show, Horace wins a door prize, an old traveling trunk which is delivered to his cottage the next day. When Gregory uses the trunk to clear away some blankets and magazines they magically disappear. Wanting to find out what has happened, Gregory slips into the trunk where he also disappears. Having no choice but to follow, Horace squeezes himself inside and closes the lid. Thus the two friends begin a journey in the land of Count Vesuvius, the sea lion king who has 'arranged' for them to visit. He demands their help to solve a mystery in his land and unless they cooperate he will not let them return home. Horace and Gregory meet friends and enemies in this tale of ocean adventure.