It is a motley crew, sitting in a private plane, invited to the mysterious Eden Island for a free week of summer vacation: A retired general, a film starlet, a professional athlete, a London rackets mobster and, last, but not least, a masked crime fighter – Captain Britain, who is curious to learn what this tropic holiday holds for the group.
They have no idea of what awaits them. In a bizarre surrounding with caged animals, a bald half-naked man with glazed eyes informs a monstrously ugly man in a wheelchair – called Doctor Claw – that the plane is arriving. The doctor announces that they needn’t hurry to greet their guests. He has surprises aplenty for them, before they met their caged pet.
Indeed, the plane lands in lush tropical surroundings… with not a soul around. The passengers debark the plane, unaware that their pilot was a robot. The pilot takes off and the passengers assume that the plane will come back for them when they are ready to leave. But, an instant later, it explodes, leaving the group to wonder how they’ll get off the island.
Suddenly, a huge insect that dwarfs them all attacks. Captain Britain asks the general to hold the group together, while he handles the creature. Captain Britain topples a tree with his star scepter and uses the trunk to dig out a defense position. After the others jump into the trench, Captain Britain creates a forcefield with his star scepter, keeping the creature at bay until it abandons its hope of a human meal and turns away.
The group is left to wonder what is going on on this island and the criminal Zampa utters the suspicion that Cap might know more about the place, as he reacted awfully quick. He’s as baffled as them, Cap shoots back, as he helps the others out of the trench. He points towards a house on a hill and suggests they’ll get their answers there. The general agrees that it sounds sensible and the group is on its way.
The actress, Julie Vane, admires a huge, tree-high flower they pass. As they speculate about the mutations in this resort, suddenly, the ground below them springs up and the flower and its base start spinning dizzily, flinging the group members off in all directions.
Julie’s frightened scream gets first response and Cap catches her and lets her down, as he rushes to the general next - the old man is sinking down in quicksilver. While the general stays admirably calm, Cap positions himself so that the other man can grab his leg and be pulled out of the quicksand.
After the general is on steady ground, Cap collects the complaining mobster from a tree, while Bert Bullard, a trained athlete, does a neat flip-over landing of his own. As they are all together again, suddenly a huge beast, seemingly an amalgation of different animals, attacks, going for Bullard first. Cap lengthens his star sceptre to a staff and it shoots out like a piston, bashing the monster’s head.
Dropping its victim, the grotesque man-beast whirls and seizes the staff. As Captain Britain braces for a tug of war, the monster suddenly shifts weight and swings him through the air. With stunning impact, the hero crashes into a tree. The creature closes in for the kill and Cap finds his sceptre out of reach. Cap’s frantic glance falls on an over-sized lizard crawling about near the tree. He grabs it and flings it at the monster. The lizard reveals monstrously sharp teeth and bites the other creature, poisoning it.
The group hurries to the house, where they are welcomed by Dr. Claw. Cap, agitated, tells him to listen. He will listen, the doctor replies. He is Dr Claw and they are his sport. Steel tentacles spring from the underbrush imprisoning the hero. As the spider said to the fly, Claw quotes, will you all walk into my parlour?