The full story
On Duckworld, a planet of humanlike ducks, Howard is pulled out of his apartment and across space, and lands in an alley in Cleveland. The first thing he does there is fight off a gang attacking Beverly Switzler, the singer in a rock band called Cherry Bomb, who takes him home for the night.
Beverly takes him to Phil Blumburtt, who she thinks is a scientist and who turns out to be a lab assistant. Howard gives up on getting home, quits a miserable job at a romance spa, and ends up managing Cherry Bomb after a brawl with their sleazy old manager. Then Phil and two colleagues turn up with an explanation: their laser spectroscope was aimed at Howard's planet when they switched it on, and it pulled him here. Run in reverse, it might send him back.
When they try, the machine malfunctions, and something else comes through. It takes over Dr. Walter Jenning, who announces himself as a Dark Overlord of the Universe, wrecks a diner with his mind, and carries Beverly off. He means to use the machine to bring another of his kind to Earth, inside her.
Howard and Phil fly to the lab in an ultralight. Their experimental neutron disintegrator drives the Overlord out of Jenning's body, and Howard destroys the creature in its real form. To make sure nothing else can come through, he blows up the spectroscope, and his only way home with it. He stays on as Beverly's manager, with Phil on the crew.