Temporarily struck blind by a flash attack, the Metal Men flee in terror from horrific, robot theme park rides. The Metal Men are led by Billy, a young blind boy, left in their charge. Counting steps, Billy retraces the path back to the Metal Men's rocket ship. En route, Mercury panics, requiring Iron and Gold to restrain him. The theme park automatons clutch at the Metal Men's rocket. Fortunately, heat friction from the rocket, as it reaches escape velocity, melts off the Metal Men's pursuers. Though Billy is able to operate the rocket's controls, from memory, the ship falls into a cosmic storm. Back on Earth, Doctor Will Magnus futilely works on a cure for Billy's blindness. Magnus is so engrossed in his work that he has not even noticed that his Metal Men, along with Billy, are gone.

As the rocket ship spins out of control, the Metal Men are tossed about the cabin. Billy manages to reverse the rocket's engines, just in time to prevent a crash landing. Most of the Metal Men are none the worse for wear. Mercury, however, has been splattered about the cabin. The Metal Men do their best to collect the globules of Mercury's body. Venturing outside the rocket, the Metal Men find that their vision has returned. Tin spies a pack of giant robots closing on their location. Platinum whisks Billy and the Metal Men out of sight, though globules of Mercury are spilled across the landscape along the way. The robot juggernauts take possession of the Metal Men's rocket. Eavesdropping on the alien machines, Gold learns that they mean to sacrifice the rocket to their Gods.

With no other way of returning to Earth, the Metal Men embark on a rescue operation to retrieve the rocket. En route, the team are caught in a strange chemical downpour. MIraculously, the chemical rain temporarily cures Billy's blindness. Suddenly, the Metal Men are attacked by a mechanical junkyard "dog". Tin molds himself into a ball, unbalancing the robot sentry. Iron and Lead then crush the sentry between them, though Tin is also pressed flat. After remolding Tin back to his normal state, the Metal Men engage one of the robot juggernauts. The monstrous machine magnetically draws the Metal Men into the grinding rollers of it's body. Desperately, Platinum pushes Billy into Tin's arms. Tin molds himself into a wheel, and rolls Billy to safety.

The Metal Men are ground and pressed into large coins. Tin tries to rescue the team, only to be caught by the same magnetic beam. While Billy and Tin helplessly watch, the Metal Men are dropped into a large smelting vat. Using the heat of the smelter, the Metal Men alloy themselves together. Melded together into a single giant Metal Man, the group quickly beats down the robot juggernauts. Reclaiming their rocket, they break orbit and depart the strange alien world. En route back to Earth, the rocket is caught in the tail of an immense comet. The Metal Men close themselves about Billy, to shield him from the cosmic rays. Arriving back at headquarters, Magnus is taken aback at his Metal Men, alloyed together as one. More surprising is that the radiation from the comet's tail has permanently restored Billy's sight.