On Hogan's Alley, all the cats are afraid of Muscles Mouse. He pounds them at will. His cousin Jerry sends a letter asking for help dealing with Tom. Muscles immediately sets out for Jerry's and upon arrival shows Tom who's boss. Tom doesn't go gently: he works out with weights to build his strength, he uses craft to launch an attack, and he calls in reinforcements. Is Muscles up to the challenge? And what will happen to Jerry when Muscles has to go home?