Mr. Hyde and the Cobra, defeated by Thor individually, decide to try working together to take revenge against the Thunder God.
Both characters were too underpowered to represent a decent threat to Thor in previous issues. Together, they make a slightly more believable threat. Mr. Hyde comes up with some scientific gadgets to even the odds a bit--including a nifty "time reversal ray" that allows them to backtrack Thor and discover he has some sort of connection with Donald Blake. The villains also make good use of a sort of tag-team approach their direct attacks, making it difficult for Thor to capture one before the other steps back into the fight.
There's one weak moment. Hyde and Cobra capture Blake to lure Thor to them. The trick Blake uses to get them to help him turn into Thor--while their backs are turned so they don't notice the transformation--was a little too contrived to be acceptable.
The story continues into the next issue. (Two-parters are slowly starting to become more common among the various Marvel books). It concludes this issue with an interesting take on how the magic inherent in Thor's hammer works. No other living being can lift it unless they are worthy, right? But can a significantly strong machine lift it? Apparently so--as Cobra uses an atomic-powered hydraulic lift to snatch it from Thor's grasp.
I wasn't sure if I liked this at first, but after thinking about it a moment, the idea grew on me. An inanimate object can't be either worthy or unworthy, so it can be argued that it is exempt from the hammer's usual magic.
The back-up story involves enemies of Asgard using a small sprite-like "air creature" to sneak past Heimdall and scout out Asgard's defences. As usual, it's Jack Kirby's magnificent art that sells this short and fairly quiet tale.