The Mystery of the Caribbean Pearls is a Biff Brewster story full of adventure and intrigue. Biff Brewster meets up by accident with Derek, after being called to the Caribbean by his Uncle Charlie. They go on to search for valuable pearls in Martinique which have been discovered by Derek's father, who is also now missing. Their adventures take them to other places in the Caribbean, and they have to avoid and deal with the evil man Dietz and his sidekicks, and also brave the dangerous waters containing sharks and other nasty things at the bottom of the sea.