The Metal Master, a humanoid alien being from planet Astra, wants to conquer the Earth. Thunderbolt Ross and his men try, but can't do much against the villain's magnetic power.
Bruce Banner decides to fight him as the Hulk, but when he uses the gamma ray machine, his body turns into the Hulk but not his head.
To keep his secret identity, Banner wears a Hulk mask and confronts the Metal Master. But the villain manages to knock the Hulk out by hitting him on the neck with a metallic object (!).
Thunderbolt Ross locks the Hulk in an extra-strong cell, but the Hulk escapes nonetheless.
The Teen Brigade, a group lead by Rick Jones, goes in the Hulk's aid. He builds a non-metallic weapon the Metal Master panics about, and leaves the Earth promissing never to come back.
Finally, Banner and Betty Ross go out on their 1st date, although her father does not approve his daughter's feeling for the "spineless milksop" Banner.