Stanley Moon, a short-order cook working at London's Wimpy's cafe, is depicted as a shy and love-struck man who harbors feelings for Margaret Spencer, a kind-hearted waitress. Despite his deep affection, his timidity prevents him from expressing his love openly, leaving him feeling hopeless and despondent. In a moment of despair, having prayed earnestly for help to win Margaret’s heart, Stanley writes a suicide note and attempts to end his life by hanging himself. Fortunately, he is interrupted by George Spiggott, a dapper and confident man who reveals himself as none other than the Devil.
George, portrayed by Peter Cook, takes Stanley to his scandalous Rendezvoid Club in Soho, where he introduces him to the case of the Seven Deadly Sins and performs mischief that underscores his mischievous nature. George admits that in these modern times, he has lost his spark, and as a gesture of goodwill, he offers Stanley a deal: he will grant him seven wishes in exchange for his soul. In return, George promises to help Stanley win Margaret’s affection.
Stanley’s first wish transforms him into an articulate and introspective individual. He invites Margaret to his apartment, where they engage in a thoughtful discussion about art, music, and their mutual love for emotional expression. Sensing her affection, Stanley tries to get closer, placing his arms around her, but Margaret panics and runs out, screaming for help. This encounter highlights the mismatch between Stanley’s newfound confidence and Margaret’s cautious nature.
With his second wish, Stanley becomes a wealthy tycoon, adorned with priceless gifts meant to impress Margaret. However, the plan backfires when Margaret becomes more captivated by a young, handsome man, revealing that wealth alone is insufficient to secure her love.
The third wish sees Stanley transformed into a popular pop singer—a move orchestrated by George to make him irresistible to women. At first, it works as Margaret and other female fans idolize him. But trouble ensues when Dremble Wedge (who bears a resemblance to George) and Vegeation begin singing, and Stanley finds himself forgotten by Margaret and the crowd, emphasizing the fleeting nature of superficial fame.
For his fourth wish, Stanley desires to be a fly on the wall, enabling him to overhear Margaret’s private thoughts about him. His plan succeeds, and he learns that Margaret speaks affectionately of him to Police Inspector Clarke, who investigates Stanley’s disappearance. When the inspector sprays bug pesticide at Stanley, hoping to kill him, George, in the form of a fly, rescues him, showcasing the absurdity and dangers of meddling with wishes.
The fifth wish is for Margaret to truly love him, be comfortable in the kitchen, and become a mother figure to his children. Sadly, this wish reveals a tragic twist when it turns out Margaret is married to Stanley’s best friend—who is, ironically, George himself. Faced with her genuine loyalty to her husband and the fact that she cannot cheat on him, Margaret calls off her relationship with Stanley, leaving him heartbroken once again.
Next, Stanley's sixth wish aims for mutual happiness and outgoing warmth between him and Margaret. Instead of achieving his goal, this wish results in both of them being transformed into nuns of the Order of the Leaping Berelians, further emphasizing the comic and surreal nature of the story.
George, contemplating his own fate, promises to return Stanley’s soul in hopes of earning entry into heaven, but God refuses him because George broke his contract for selfish reasons. George then asks Stanley to sign a new, temporary contract so he can retrieve his soul later, but Stanley, realizing George’s promises are unreliable and his motives selfish, refuses.
Deciding to face his destiny unaided, Stanley chooses to approach Margaret without any magical help. Throughout the story, George continues to tempt him, claiming he will make the world so noisy and repulsive that even God would be ashamed of it. The narrative ends on a humorous note, highlighting the absurdity and moral lessons about greed, superficiality, and the importance of sincerity.
Throughout this fantastical journey, the film explores themes of desire, temptation, and the consequences of wishing for what may seem desirable on the surface but could lead to unforeseen complications. It’s a satirical and whimsical tale about a man’s quest for love and the devil’s mischievous interventions, with sharp humor and a playful tone that satirizes modern society's obsession with superficial glamour and materialism.