Zandor goes to find out what made the flying monkeys panic and lands on a web of a Venom Spider. Zandor is able to fire his slingshot at it. Zok and Dorno find Zandor laying on the ground and Tara meets them there and tells them that he badly injured. Dorno sees that he has been stung by the Venom Spider. The only ones that know an antidote are the Spidermen of the Endless Caves. Dorno vows that he and the Herculoids will retrieve the antidote and cure Zandor.
They reach the entrance to the caves and Dorno tells the Herculoids that he will go in alone to get the antidote and tells Igoo and Gloop to watch and make sure nothing happens. Dorno goes in and is trapped and captured by the Spidermen. Gloop enters the cave and finds out what the Spidermen are up to and signals the rest of the Herculoids. Igoo tears out the door to the cave and the Herculoids charge in. Igoo finds Dorno and frees him.
The Spidermen use a flame wall to stop the Herculoids. Igoo and Dorno are trapped by the flames and Gloop rescues them. Zok then puts out the flames with his laser beams. They then rush in to get the antidote. One of the Spidermen grabs the antidote to bring it to the leader, and he is stopped by Gloop, and Dorno grabs the antidote. The leader calls out the guards and a brief fight erupts with the Herculoids defeating the guards. Dorno and the Herculoids are trying to leave the caves and are chased by a bunch of the Spidermen on Venom Spiders. Once outside, the Herculoids use a boulder to block the entrance to the caves.
Dorno and the Herculoids get the antidote to Zandor and they use it. Zandor recovers and thanks Dorno and the Herculoids for getting the antidote.