Ukridge and his pal Jimmy Corcoran are taking a break in the country, and one night Ukridge decides to tell the story of Mabel and the top hat. Ukridge had met Mabel at a dinner party at his Aunt Julia's house, and had fallen for her hard; she was the daughter of a wealthy colonial type who was busy out in Singapore, and Ukridge began frequenting their house.
He has a rival for Mabel's love, who is a Baronet, which worries Ukridge somewhat, but he is given confidence by his dress, which, as he is at the time staying with his aunt, is rather dapper, top hat, spats and all. Ascot is approaching, and Ukridge agrees to attend with Mabel and her family.
Aunt Julia discovers that Ukridge has pawned a clock from the spare room, to pay for gifts for Mabel, and kicks him out once more; Ukridge takes lodgings, but one day his hat is blown off and crushed in the street. Needing one for Ascot, he approaches George Tupper for a loan, but Tupper, annoyed at Ukridge for touching him twice in a week, proposes to find Ukridge a job, and fixes up a meeting with a friend of his who is after a secretary. Ukridge agrees, but on the way out picks up Tupper's topper.
The day of the races arrives, and Ukridge gives his coat and hat to his landlady to clean up ready for the big event. She holds them to ransom, refusing to return them unless he pays the back-rent he owes. Desperate for apparel to attend the meet, he has a visitor, who he takes to be Tupper's friend come to interview him for the job; he tricks the man out of his coat and hat, which fit like a charm, and heads off to Ascot.
Arriving, he meets Tupper, who tells him the friend had to cancel their appointment and had left for Paris the previous evening. Ukridge is bemused, until Mabel asks where her father is - he had, apparently, returned early from Singapore, and had been sent to collect Ukridge and bring him along to Ascot. Having thus embarrassed himself in front of her father, Ukridge gives Mabel up, and hears she later married the Bart.
Ukridge suggests a weighty, moving title for the tale, something about fate and destiny, but Corky has something more fitting in mind...