Jumbo Comics #110

Sheena and Bob rescue Sylvia, under attack by natives, and they offer to escort her. While Sheena is separated from them, Bob and Sylvia are taken prisoner; Sheena rescues them but their canoe is attacked by a giant squid. It turns out to be a submarine, which brings Bob and Sylvia to the hidden island where Brad Carter rules supreme. Sylvia tries to ransom her father off the island, Carter plans to kill them all, Bob, Sylvia, and her father escape in the sub and Sheena battles Carter to his death.