This is an example of a fun Jerry Siegel story, with no glaring plot holes or scientific gaffes. The plot is straightforward: a teen Lex Luthor (with a full head of hair) comes forward in his “time cylinder” to meet his idols, the Legion of Super-Heroes, whom he’s observed on his timescope.
Okay, it’s not a scientific gaffe, but it does defy belief that a teen Lex Luthor created two devices that it took the rest of the human race 1,000 years to develop, as witnessed by the fact that they’re still considered pretty rare and nifty in the Legion’s time.
The Legion quickly realize that this charming, innocent boy, who has saved Triplicate Girl and Matter-Eater Lad from death at the hands of the inhabitants of the planet Khann! (established as a penal colony by the William Shatner fan club, no doubt), is actually Lex from before the time that his hair fell out, resulting in his conversion to villainy.
As promised at the end of “The Army of Living Kryptonite Men”, an adult Lex Luthor, imprisoned, makes good on his promise to track down the Legion of Super-Villains, which must exist, he reasons, if there is a Legion of Super-Heroes. His method of tracking them down is pretty hilarious—he offers to repair all of his fellow inmates’ broken radios, and, while doing so, steals one part from each of them in order to build a future transmitter. Did the radios with missing parts actually work when he was done? We’re never told. I guess it doesn’t matter, since, after building the future transmitter, he quickly secures the means to escape.
“Calling the future!” he says into his transmitter. (I love it!) These were the days, if you don’t remember them, when a lot of Americans still didn’t dial phones. They picked them up and told an operator who they wanted to talk to. So Lex wasn’t behaving that out of character for someone of his time, but still… The whole future, Lex? All of it?