In the dead of night, a little mouse in diapers named Nibbles arrives in medieval Paris, brandishing a broken sword. He is the son of Francis Mouse, sent by his father to seek out the skilled swordsman Jerry and learn the art of fencing. Whether due to his young age or lack of talent, Nibbles flails about wildly, turning Jerry's room into a complete mess. However, since it's a request from an old friend, Jerry reluctantly agrees to take on this apprentice, despite his thousand reservations. He even takes the little one out for a stroll, during which they naturally cause plenty of laughter and nearly become a meal for the veteran swordsman cat. Unable to bear it any longer, Jerry writes a letter to his old friend and promptly sends Nibbles away. Dejected, Nibbles leaves on his own, only to witness Tom and Jerry engaged in a wildly mismatched battle. Fearless as a newborn calf, the little one charges straight into the fray...