Two boys, Johnny and Scott, were playing on the beach one day when they "meet" Sigmund, a green sea monster with tentacles who looks like moving seaweed. As it turns out, Sigmund got tired of his family who wanted him to become a "proper" sea monster (i.e., scaring people etc), and as a result, he ran away from home. Johnny and Scott decided to take him home with them, and decide to hide him in their clubhouse hoping that the housekeeper Zelda (who looks after them while their parents [whom we never see] are away) never finds him. Meanwhile, Signmund's family, who lives at "Dead Man's Point", is constantly scheming different ways to bring Sigmund back home, one way or the other. Signmund's brothers, Blurp and Slurp, are always trying to forcibly take Sigmund back with them, but their plans never work...