Adventures Of The Super Sons #10
It's the runaway train from hell! Superboy and Robin better hold on for dear life as they ride a 20-megaton cosmic engine of mass combustion (that's a pun!) into their final battle with Rex Luthor! But Rex has got a brand-new army of shiny young super-villains ready to conquer all they survey...will the son of Batman and the son of Superman be enough to stop him?