Part One – Enter the Toad Men
The Hulk (now green in color) is seen staggering out of a swamp by a local police officer who races off to alert the town that the monster is nearby. The Hulk responds to the local’s attempts to subdue him with violence but is eventually coaxed off the battlefield by Rick Jones. Meanwhile, the Earth is about to get several strange new visitors (the Toad Men) who armed with advanced magnetic technology beyond human understanding use a 'magnetic grappler' to lock on to Dr. Banner’s vast scientific mind and land nearby to capture him. Their intention is to capture the smartest man on the planet and force him to reveal how far the planet has come technologically.
Bruce and Rick meanwhile are preparing an underground cave with an isolation chamber in which to trap the Hulk each night before the transformation occurs. Suddenly their process is interrupted when they are captured by the toad men from outer space!
Part Two – Prisoners of the Toad Men!
Trapped by the toad men's magnetic ray guns, Bruce and Rick are transported to the toad men’s spaceship and rocketed out of Earth’s atmosphere. Captain Torrak of the toad men explains that Bruce and Rick are his prisoners and that Earth is surrounded by their invincible fleet. Demanding the technological knowledge of the Earth he threatens to use their magnetic powers to knock cities free of the planet’s crust, empty the world’s oceans of life, or root everyone to the ground preventing them from moving.
The toad men realizing that Rick is of no value and transport him safely back to Earth but as the ship moves to the dark side of the Earth, the transformation begins and Bruce Banner once again becomes the brutish Hulk. The Hulk breaks free of his confinement and attacks his captors and realizes that with the toad men’s weaponry, he could wipe out all of mankind once and for all Just then the U.S. Anti-Missile Base below detects the ship in the night sky and fires on it and the UFO crashes to the ground as General Ross and his men surround it.
Part Three – Bruce Banner, Wanted for Treason
As the military officers move in to investigate the crashed ship, a bedraggled Bruce Banner stumbles free and the surviving toad men escape via a tunnel they blast under their ship. Bruce Banner is then taken into custody and once in the clear the toad men on the surface send a flare into the sky to signal their armada to attack. The sky is soon fills with the ships of the toad men fleet from outer space.
Part Four – Hulk Runs Amok
The toad king contacts the Earth and warns humanity that his forces are preparing to shift the moon toward Earth using their magnetic powers. This will eventually lead to the destruction of Earth unless mankind surrenders. Meanwhile, the night falls and Bruce Banner once again turns into the Hulk. The Hulk escaping his captivity, sets off in search of General Ross who imprisoned him but instead comes upon Betty alone in the Ross house. Betty screams as the army attacks the Hulk in an attempt to rescue Betty from him.
Part Five – The End of the Hulk
The Hulk manages to escape capture and takes Betty as a hostage. Rick figures that the Hulk must have taken Betty back to Banner’s Lab and makes his way there as the Hulk explains to Betty that he hates humanity for what they have done to him. Rick confronts the Hulk but before the Hulk can silence Rick forever a tremor from the toad men’s magnetic weapons shakes the lab knocking all three unconscious.
As the sun rises, it is who Banner awakes first and along with Rick runs to the storage site of the gamma ray gun. Bruce then fires at the toad men’s ships and the blast of energy causes them to lost control of their movement and hurtle out of control into the void forever. Banner is regarded a hero for saving the Earth but General Ross remains skeptical believing he is somehow connected to the Hulk.