Stan and Ollie find themselves tasked with washing dishes by Ollie's wife, initiating a series of mishaps. Stan's overly generous application of liquid detergent results in an excessively thick washing solution, leading to further complications as Ollie attempts to handle the dishes. Their interaction with James Finlayson, who arrives to collect payment for furniture, devolves into a convoluted dialogue regarding monetary exchanges.

In a bid to resolve the situation, Ollie withdraws their savings to purchase furniture, inadvertently squandering the majority of the funds on a grandfather clock at an auction, only for it to be destroyed shortly thereafter. Facing the repercussions at home, Ollie becomes the victim of a frying pan assault by his wife, resulting in serious injuries requiring a hospital visit.

The doctor enlists Stan as an unwilling blood donor for Ollie's transfusion, leading to a series of comical errors with the blood transfusion equipment. The machine malfunctions, causing an exchange of blood between the two, ultimately culminating in the machine's explosion. Upon exiting the hospital, Stan and Ollie discover that their physical appearances have been interchanged, prompting them to engage in humorous imitations of each other's mannerisms. Their departure from the hospital is punctuated by the characters comically embodying each other's identities, including vocal mannerisms and signature catchphrases.

At three points in the film, Laurel and Hardy drag the next scene into the frame from off-camera. This effect was achieved with the optical-printing device known as a wipe.

• Thicker than Water at IMDb  
• Thicker than Water at the TCM Movie Database