Popeye is trying to get his nephews to eat their spinach, so he tells them about how Hercules (Popeye) defeated a bully (Bluto).
Hercules gets his strength by sniffing garlic; he wins numerous tests of strength against the bully until the bully spots him sniffing garlic. The bully pulls out a handy bottle of chlorophyll and douses the garlic, disabling Hercules. He then knocks him into a field of spinach where Hercules discovers a new and better source of strength.