Deranged scientist Professor Noodle is engrossed in developing a rejuvenation elixir for over two decades, purportedly capable of reversing the aging process. Stan and Oliver, employed as chimney sweeps, enter the scene, assigned to cleanse the estate's chimney. As Oliver ascends to the rooftop, Stan, stationed below, inadvertently propels the sweep upwards, causing Oliver to tumble through the skylight. Following an arduous exchange, Stan eventually joins Oliver atop the roof, albeit mishandling the apparatus, causing a disruption in the chimney's extension. Subsequently, resorting to a rifle for assistance, Stan nearly endangers Oliver's life in a botched attempt.
In a series of calamitous events, Stan's clumsiness results in Oliver's fall from the rooftop, damaging property and inciting chaos within the household. Amidst the tumult, Professor Noodle endeavors to demonstrate his rejuvenation solution, commencing with the transformation of a duck into a duckling through a solitary drop of his concoction. Encountering an opportunity, Stan and Oliver clandestinely endeavor to experiment with the solution, leading to a catastrophe as Oliver, perched atop a stepladder, and the solution container plunge into the vat.
The ensuing pandemonium witnesses Oliver's transformation into a chimpanzee. Despite his devolution into a primal state, Oliver's recalcitrance remains unchanged.