Forbidden

Jim Harding, a trained chemist, earns a living selling potions and medicines from a portable stall on the Blackpool fairground, accompanied by his former army colleague Dan Collins. The duo uses their craft to make ends meet while the fairground atmosphere hums around them. This modest life grounds Jim as he navigates a future he didn't intend.

Jim's marriage to Diana is unhappy and stifling, with her domineering, ambitious nature driving a wedge between them. Diana harbors theatrical ambitions and treats Jim as a means to an end rather than a partner. Jim experiences growing dissatisfaction, feeling trapped in a relationship that offers him little affection or respect.

Attracted to the kinder, working-class Jane Thompson, Jim starts an affair that promises warmth and companionship he lacks at home. They meet at a nearby stall where Jane sells candyfloss and ice cream, and the bond deepens despite the risk of exposure. Jim does not reveal his married status as their relationship blossoms.

While Jim pursues Jane, Diana pursues her theatrical ambitions through an ongoing liaison with the older Jerry Burns. She believes Burns can help advance her career, and she uses the arrangement to bolster her own standing. The parallel affair adds to the tension and motives in the couple's broken marriage.

Diana discovers Jane's existence and visits Jane's home to reveal Jim's married status, trying to persuade Jane to end the affair. She even offers cash, hoping to buy Jim's lover's silence and secure her own path to the stage. Jane refuses to be bought, setting the stage for a confrontation with Jim.

Jane confronts Jim about the betrayal, and he explains that he is trapped in an unhappy marriage with a selfish wife. Jim asks for a divorce, but Diana refuses to split, fearing it would jeopardize her career. The confrontation deepens the sense of inevitability about Jim's grim options.

In desperation, Jim decides that the only way out is to remove Diana from his life by killing her. He studies her medical history, including a thyroid illness and medication habits, hoping to exploit weak points. The plan marks a dark turning point as he contemplates murder.

Using his chemistry knowledge, Jim concocts pills containing a lethal dose that could appear as part of Diana's regular medicines. He carefully prepares the potions in his workshop, trying to keep the plan from his own knowledge and conscience. The act marks a chilling prelude to murder.

In a panic after Diana's death, Jim buries her body beneath the floorboards in his workshop to hide the crime. He believes his carefully laid trap has silenced his problem at last. Later events reveal a troubling twist about the true cause of her death.

During later clearing of the bedroom, Jim realizes the pills he made were never used and that Diana died of natural causes. The disposal of her body becomes incriminating rather than protective, forcing Jim to confront the consequences of his actions. The turn of events twists the situation into a more dangerous predicament.

Diana's unexplained disappearance triggers police suspicion, as investigators deduce that she was killed by her husband. Jim becomes the prime suspect, and the evidence mounts against him. His attempts to maintain his freedom are complicated by the growing case against him.

Panicked by the growing investigation, Jim tries to flee, chased through the streets of Blackpool. The pursuit culminates in a final confrontation at Blackpool Tower, bringing the tragedy to a head. The chase binds together the fraudulence of his life with the town's looming symbol of fate.