When local musical prodigy, Gilbert Swann, is selected to play the violoncello with the visiting London orchestra during the musical festival in the five towns, his mother is convinced that he will be the cornerstone of the entire event.

When local dignitary Mrs. Clayton-Vernon invites Gilbert to dinner before the concert with her cousin, the famous conductor from London, she sees this as recognition of his musical genius. A sudden cold snap on the day, however, makes Mrs. Swann fearful that Gilbert's hands will get cold on the journey from Mrs. Clayton-Vernon's house to the concert.

She resolves to deploy a remedy from her childhood, and sets off to Mrs. Clayton-Vernon's mansion with two steaming hot baked potatoes hidden in her muff, for Gilbert to warm his hands upon before the concert. It does not occur to Mrs. Swann initially that smuggling hot potatoes into Mrs. Clayton-Vernon's grand house may be considered a social faux-pas. Her efforts to conceal the potatoes and hand them over discretely to her son are deliciously farcical...and the adventure turns out rather differently than intended.