Superman makes a television appearance, in which he announces that he's just learned his life is in particularly serious danger. He buries a large vault, containing his last gift to the world--something that will benefit mankind as much as his superpowers. The lock to the vault is synched to his heartbeat. If he dies, the vault will open. The vault is made of impenetrable "Supermanium," so (theoretically) no one can break into it.
But back at this secret headquarters, after he
At which point, Superman flies out, thanks Luthor for rescuing him, then knocks the criminal and his henchmen unconscious.
The explanation? The vault was actually a trap set by Mordru, the evil wizard from the 30th Century. Mordru used magic to lure Superman into the vault and hypnotize him to keep him from breaking out. Only someone with super strength of a Kryptonian level could break him free--but the magic would lure Supergirl into the trap as well if she approached.
Using Super-Ventriloquism, Superman contacted Supergirl and suggested she call in the Legion of Superheroes for help. The "Superman" that Luthor "killed" was Braniac 5 in disguise, using his
It's a fun story, written by Cary Bates (one of my favorite Silver Age writers--he had a real sense of what made comics fun to read.) The pencils are by the legendary Curt Swan--whose crisp, clean art made him an expert visual storyteller. You never have any trouble at all following the plot or action in a Swan-illustrated story. In this issue, the design of Luthor's various devices (robots, mole machines, etc.) are particularly fun.
There is, I suppose, one obvious plot hole. Superman needed a super-genius to figure out how to break open the vault. That's all well and good. But didn't he have a super-genius available in the form of Braniac 5, making the complex plan to fool Luthor unnecessary? Oh, well, I suppose the story is implying that Luthor is even smarter than B5.
Also, it's too bad there was no sequel. At the end, it's mentioned that other members of the Legion had tracked down and defeated Mordru. All that happened "off-screen," though. It would have been fun to have a follow-up issue showing Superman teaming up with the adult Legion to do battle with Mordru.
But despite a few minor flaws, this is a nifty Superman story that highlights how much fun the Man of Steel can be when properly handled. Superman, Supergirl and the Legion effectively run a Mission:Impossible-style con on Luthor. It's a great example of how a clever writer can write an interesting Superman story despite his seemingly infinite power levels.