Sylvester, voiced by Mel Blanc, sleeps downstairs as the clockwork rhythm of a lighthouse ticks into the night on a small island. The pendulum’s rhythm nudges the beacon’s light into a mouse-hole downstairs, leaving the resident mouse wide awake. The daredevil rodent creeps out of bed, climbs the stairs to the beacon, and yanks the plug out of the outlet to turn the light off. Polly the parrot dives into the light-keeper’s bedroom, squawking “Light's out! Light's out!” and setting off a chain of comic mishaps. The light-keeper wakes with a growl, exclaiming, “Grrrreat Scott! It's that crrrrazy moose (mouse) again!” and the two adults soon discover a cargo carrier named Australia has crashed into the rocks, dumping several wooden crates overboard. The furious captain scolds the light-keeper to keep the beacon lit, while the light-keeper and Polly apologize for the chaos. Inside one of the crates lies Hippety Hopper, a baby kangaroo bound for a city zoo, who hops free when the crate breaks apart against the rocks after the ship sails away.
As this chaos unfolds, Sylvester remains downstairs, but the light-keeper’s impatience is loud: “While you sleep, that crrrrazy moose is loose in the hoose!” Polly echoes the command, and Sylvester is dispatched upstairs to capture the elusive mouse. Hippety hops into the lighthouse and follows Sylvester up the stairs. A mousetrap is set, and a clever string attached to the trap leads Sylvester to a sensational mistake: he believes he has trapped a giant mouse, only to discover he has actually captured Hippety. The jaw-dropping moment sends him tumbling down the stairs as Polly continues counting the seconds—an absurd tally that stretches into what feels like an entire day.
The mouse, ever sly, frees Hippety from the trap and retaliates by pulling the electric plug again, plunging the lighthouse into darkness. Sylvester races back up, pleading with Polly to keep counting, while attempting to reconnect the cord and secure the system. He fumbles with nails over the outlet and braces himself for a confrontation, but the shadow of Hippety’s looming presence gives him a scare, and he charges toward the elevator only to collide with the mischievous duo behind the door. A playful back-and-forth between Hippety and the mouse escalates into a physical chase, and Sylvester ends up tossed by Hippety when they surge through the door.
The light is restored only briefly as the prankish duo again pulls the extension cord from the wall. The light-keeper corners Sylvester with a Shillelagh, threatening to “fix that good-fer-nothin’ pussycat.” From above, Sylvester watches as the animal pair works their mischief and contemplates a more permanent solution to the problem. With a desperate improvisation, he becomes a makeshift conductor, bridging the two severed ends of the cord and delivering a massive electric jolt that powers the beacon again—“Lights on! Lights on! Lights on!”—even as the light-keeper restores calm on the stairs.
But the danger isn’t over. The mouse rigs a dynamite stick with the cord wound around it, the hiss of the fuse filling the air. Realizing the doom that awaits, Sylvester retreats in terror as the fuse burns down. The explosion destroys the cord beyond repair, leaving Sylvester singed and stunned. The light-keeper bursts back into the scene and pummels him with a huge club rather than just a Shillelagh, ending the immediate threat with a comic burst of physical humor.
In the final moment, the lighthouse settles into a peaceful rhythm again. The light-keeper, Polly, Hippety, and the mouse drift into a contented sleep, while Sylvester becomes the beacon himself—hooked up to a battery, his eyes projecting the guiding light for the island. He mutters with a resigned humor, “I never thought just being a pussycat could be so complicated!”
