A grateful mouse promises Felix "if there's anything I can do for you, just call on me" after Felix lets him go from a mousetrap. Felix then goes over to Willie Brown's house, whistles for the kid to come down from his bedroom and go "to the 'ole swimming hole" but Willie's mom spots him and tells the boy to go back inside and "practise his piano lessons." (That's the way they spelled "practice" in the cartoon, which often uses bubbles for dialog the way they do in printed comics.
A dejected Felix goes back to the barn area, where we first saw him with the mouse. He explains his dilemma to the mouse who has a plan to help out the cat and get the kid out of doing his piano lessons. That plan - have four other mice jump around on the piano keys and make music - is funny and leads to some very humorous dancing scenes with Willie's mother, who thinks her son now is Liberace.
Overall, this was good and offered a number of surprises, which a couple of more grammatical errors in the cartoon's dialog boxes.
This cartoon was part of a collection of in the "Presenting Felix The Cat - The Otto Messmer Classics - 1919-1924" DVD, with original organ scores by Dave Wickersham.