在这部杰瑞的表兄喜剧/动画/短片/家庭片中,在一座大城市的阴暗角落，正发生一场激烈的拳脚打斗。几只野猫遭到无情的打击，全然丧失抵抗能力，而施暴者竟是一只身材矮小却蛮力过人的小老鼠——马索（Muscle）。在收拾过老猫后，马索察看门前的信件，发现了远方表弟杰瑞寄来的信。信中杰瑞痛陈被汤姆欺压蹂躏的始末，并衷心地向表哥求助。亲戚有难，自然应责无旁贷地出手相助。马索即刻收拾行囊启程，一路上所有的猫都闻风丧胆，早早躲藏起来。
与此同时，杰瑞正被汤姆逼在洞中戏耍，表哥的出现给他生的希望。当然，汤姆不会将马索放在眼里，可是他很快便发现眼前这个和杰瑞一模一样的小家伙，却有着极其强大的战斗力……
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?
