The Hulk has been captured by the Collector after a titanic battle against his slaves, the Glob and Man-Thing in the Florida Everglades. Taken to the Collector's ship, the Hulk is placed inside one of his habitats and is shackled with a device that prevents him from escaping. He is put on display in a swamp like environment with both the Glob and Man-Thing. In "payment" for helping the Collector capture the Hulk, Captain Cutlass and his pirates are returned to the miniature ship in a bottle they have been prisoner in for hundreds of years since the Collector first captured them.
Left to slumber in his new habitat, the Hulk reverts back to his Bruce Banner form. Since the leg shackle was designed to fit the Hulk, Banner easily slips it off and leaves the habitat and begins exploring where he is. Banner finds to his horror that the Collector has captured an enslaved many beings from Earth and other worlds from various points in history and has made them all his slaves for his own personal museum. Listening to their pleas, Banner agrees to try and free them from their captivity. As Banner rushes off, he runs into the Collector who recognizes the Hulk's alter ego and offers him a proposition.
Back at Hulkbuster Base, General Ross meets with Clay Quartermain to tell him that the base has been officially retitled and reclassified as Gamma Base where they would expand their focus on trying to cure all creatures mutated by gamma radiation, and not just hunt down the Hulk. Ross happily informs Clay that he has been appointed SHIELD liaison at Gamma Base. Looking out the window, Clay spots Doc Samson out on another walk with Betty Talbot, and comments grimly that he finds his new assignment is "just swell."
Back aboard the Collector's ship, the Collector shows Banner around his ship and shows him his first line of defense should any of his prisoners escape: Akbar, former bodyguard of Kubla Khan. The Collector explains to Banner that his travels have been lonely and that he seeks a companion to travel the stars with and offers Banner that position, offering to cure him of being the Hulk. Deciding that he has nothing to hold him on Earth, Banner accepts. When the Man-Thing and Glob manage to escape from their cells (Their shackles slip off their mailable forms) it sets off an alarm. Hearing the Collector refer to the people he has captured as merely "exhibits", Banner changes his mind on his offer forcing the Collector to set Akbar on him.
Banner transforms into the Hulk and easily fights off the barbarian warrior, and sets his sights on the Collector. When the Collector offers the Hulk the serum to change him back into Bruce Banner, the Hulk angrily smashes the vial and continues his advance. The Collector seals the Hulk in a powerful force field, and when the Glob and Man-Thing arrive on the scene, sends an army of various creatures and humans from different time periods under his control against them. As the battle rages on, the Hulk manages to free himself and join the fight, causing damage to the controls that kept the Collectors prisoners trapped. In the confusion, the Collector makes his escape and the princess that convinced Banner to try and free them manages to talk everyone into stopping the fight. They all free the ship as the Collector flees to repair his ship and prevent his captives from escaping. The Glob follows after him and seemingly kills him, stopping his efforts to stop them.
As the captors escape outside, the man years of captivity catch up with them as they begin to rapidly age once outside of the ship. As the princess thanks the Hulk for freeing them -- as death was a better choice than eternal slavery -- the Man-Thing shambles off into the swamp leaving the Hulk to try and make sense of what he has just witnessed.