In Venice to retrieve the ransom money paid to Doctor William Magnus, the Metal Men run afoul of several robot guards. After dispatching the sentries, the Metal Men arrive at the proper building to find... nothing. The vault with the ransom money is gone. Before they can determine their next move, they are surrounded by the Venice Police Force. Eight weeks prior, Magnus had just finished reconstruction of the Metal Men, after they had been destroyed in combat with the Plutonium Man. A glitch in Platinum's responsometer switched her affections, normally reserved for Magnus, to the other Metal Men. Before Magnus could look into the matter, General Caspar burst into the lab, demanding Magnus return the ransom money, paid to Magnus during a blackmail scheme. Magnus, though, had no recollection as to where he'd hidden the money. Scanning Magnus's subconscious revealed that the money was in Venice.
The Metal Men were sent ahead to retrieve it, encountering Magnus' robot sentries. Magnus arrives and clears the matter up with the Venice police. The two people Magnus left to look after the ransom money, Francesca and Raimondo, have, in fact, stolen it. Raimondo feverishly tries to crack the lock that will allow him to claim the money, from the vault's true guard, Chemo. Raimondo shatters Magnus' control device, unleashing Chemo on Venice. Chemo's first act is to hurl the vault with the ransom money into orbit. Turning on the Metal Men, Chemo spews a metal dissolving acid that consumes Gold, and horribly injures Magnus. Meanwhile, in Washington D.C. a would-be mugger gets more than he bargained for, when his chosen victim incinerates him. That chosen victim identifies himself as "Doctor Will Magnus". With Magnus and Gold incapacitated, Iron takes over the leadership of the Metal Men.
Though Magnus' last order was to retrieve the ransom money, Chemo's threat to Venice takes priority. Tin outlines a plan for taking down Chemo. Engaging Chemo, Platinum leads the attack by winding herself about the chemical horror's limbs, binding him. Tin then reduces himself to tin pest, the better to coat Chemo. Iron hurls Lead at Chemo's head. The soft, dense Metal Man smothers Chemo's head, while Mercury also binds Chemo. Though Lead, Mercury and Tin perish in the assault, their attack distracts Chemo from the real threat... Iron. Molding himself into a drill, Iron burrows into Chemo's ankle, releasing Chemo's liquid form into the Venetian canals. Once the liquid level drops below Chemo's mouth, Iron and Platinum mold themselves into a spring-loaded hammer, and shatter Chemo's glassine form. Magnus revives, just in time to hear Platinum give him the "good" news. She and Iron are getting married.