After the Clara was blown up by Barnaby, Clark, Jimmy, and their new friend Pug Flanagan await passage from Panama back to the United States. Until now Clark has always tried to play it off as though Superman were a figment of Jimmy’s imagination, or doesn’t exist, but after the dramatic rescue in the previous adventure, he has a harder time shirking it off.
As our trio await word from Perry about their next mission, shady characters plan to take the treasure map that Jimmy has. The leverage that Carlos has over his henchman seems silly, going to prison over detaining or opening a letter, but up until this era it was common to send money and valuables through the mail. It was the safest way to send it. You can see how important it was to safeguard it, and enforce infractions of taking it.