Daffy is an assistant to a Mexican scientist who has just built a time machine and gone to take a siesta. Daffy is annoyed by Speedy and his band playing music right outside the laboratory window so he hatches a plan to send him back in time to be rid of him. He lures the mouse into the machine by telling him it's a recording booth, but when he activates it he accidentally sends himself too and they both wind up in ancient Rome. Daffy yells at a passing gladiator who doesn't take kindly to it and promptly throws both of them into the Colosseum. Emperor Nero and the rest of the audience laugh as a lion also enters the arena. They fight back and forth until the lion flings them into Nero, breaking his fiddle. He chases them through the streets of Rome. Meanwhile, the scientist wakes up and reverses the time machine to bring Daffy and Speedy back, but he accidentally brings Nero to the present too. Nero doesn't know what he's going to do here, so Speedy lets him play fiddle in his band, outside the lab window.