Romantic, impoverished Michael Gore-Brown is embarrassed in a Mayfair florist's when he cannot afford 15 guineas for a floral display. His cousin, Sir Henry Hazelrigg, enters the shop to tell him that a relative has died and bequeathed Michael a Mayfair ladies' dress salon.

Henry suggests he sells the business without delay, and warns Michael about the likely dragon of a 'manageress'. Alone, Michael checks out the lavish premises of Maison Londres. In the foyer, he collides with attractive Eileen Grahame, without realising that she is the manageress, and introduces himself. He decides to take a lively interest in running the business, reluctantly supported by Henry.

In a nearby salon, Eileen's business rival, D'Arcy Davenport, serenades his wealthy clients, after which they need smelling salts to recover. At lunch in a Mayfair restaurant, Eileen, Michael and Sir Henry are spotted by D'Arcy, who introduces himself. Later, at Les Ambassadeurs club, Eileen dances with D'Arcy who offers her a business partnership, which she declines. Michael tries to attract her attention throughout the evening, leaving and then returning to the club.

At Maison Londres, Eileen wants to talk business and designs, but Michael insults wealthy lady customers, such as Mrs Anstruther, who take their custom to D'Arcy. He is also a disaster with tape measurements.

D'Arcy expects Maison Londres to be sold at a knockdown price soon, and plots with two spivs, Mr Keats and Mr Shelley, to bring about its demise.

Eileen is reluctant to let Michael see her new designs, but she relents and explains how various designs become reality in the pages of Vogue. Her top secret is that the 'New Look' skirts are going to be 13 inches from the ground - this is overheard by Sir Henry, and she asks him to keep this information strictly confidential.

Michael and Eileen dance in an elegant nightclub, and find themselves attracted to each other. She invites him home.

Sir Henry, after getting drunk at Burke's military gentlemen's club in the company of D'Arcy, is charged with being drunk and disorderly at Savile Row police station. Michael agrees to stand bail, and takes Sir Henry home with him. Michael dreams about fashion and how designs are transformed into ladies' clothes. The following morning he sees a Daily Express headline revealing that the 'New Look' for the season is no longer secret, and shows the paper to Sir Henry, who admits responsibility. Eileen, unaware of the leak until the Express phones , assumes Michael is responsible. This is a such a commercial disaster for Maison Londres that she visits D'Arcy and accepts his offer of a business partnership.

D'Arcy is off to Paris to view the new collections and Eileen goes as well. In Paris she places a telephone call to Michael who, unbeknown to her, is in an adjoining hotel room. D'Arcy and Eileen visit large open- air cafe. She suggests 'Maytime in Mayfair' as a name for his new perfume, but her thoughts are elsewhere, romantically thinking of Michael and Mayfair. Returing to harsh reality, D'Arcy shows her a telegram stating that Michael is prepared to sell the business to him at any price.

Eileen leaves immediately for London. At Maison Londres Michael is about to 'give the business away' to Keats and Shelley. Eileen says she is not selling, threatens to phone Scotland Yard, and tells Michael to kick them out. She discovers that the leak was from Sir Henry, who was plied with drink at Burkes club by ' D'Arcy . Michael decides to settle the score with D'Arcy.

The Savile Row police sergeant phones Eileen to tell her that he has Michael in custody. She arrives to stand bail. Michael has been charged with assault and battery on D'Arcy, who lies injured in a hospital bed. By agreement, the charges are withdrawn. On entering his cell , Eileen sees that Michael has drawn a Norman Hartnell wedding dress on the wall...

After the wedding of Michael and Eileen, cheering crowds see them off. Among the well- wishers is Sir Henry, who announces 'The End' to the Savile Row police inspector.