The AMAZING SPIDER-MAN is trapped in an underground fighting tournament, courtesy of THE MANDARIN! THEN! Spidey's caught up in a calamitous caper with the BLACK CAT to capture the elusive FROG MAN!
In the first story, Spidey runs into some guys beating up on one guy. Spidey helps the guy, who was supposed to be pressed into an underground fighting tournament run by the Mandarin. When the Mandarin shows up, Spidey agrees to take the guy's place.
Spidey beats up a bunch of second- (and probably fifth-) rate guys, including Kangaroo and Constrictor over six rounds. In the last round he has to fight the Mandarin himself. He survives for a while but clearly can't beat the powerful Iron Man villain. So he uses his back-up plan, and calls in the Avengers, who settle things quickly.
In the second story, Blonde Phantom hires Spidey to catch Frog-Man. He catches Frog-Man quickly after he robs some jewelry. However the Black Cat shows up and steals both Frog-Man and the jewelry. Spidey chases after her, but her bad luck powers keep making him run into all kinds of unfortunate accidents.
When he finally catches up, she gives him a phone, over which the Blond Phantom tells him that she had also asked Felicia to catch Frog-Man. Black Cat just had him chase her for fun. She splits the reward with him.