Portrait of Alison

A car plunges over a cliff in Italy, killing newspaperman Lewis Forrester and actress Alison Ford. The tragedy immediately frames the mystery that will unfold in London. The crash hints at a larger conspiracy involving people close to the victims.

In London, Tim works as an artist and paints his favourite model Jill for a beer advertisement. Jill reveals she is trying to settle down, having previously dated Tim and now dating Henry Carmichael. Before a police inspector arrives, Jill and Tim share a passionate moment, underscoring their complicated history.

Tim receives an unusual commission from a Mr Smith to paint Smith's dead daughter Alison. He is supplied with a photo to work from and a pink dress for the portrait. The assignment unsettles Tim, who senses a link to the earlier crash.

Jill spots the pink dress and the portrait and admires both, hinting at deeper motives behind the commission. She goes to meet her fiancé for lunch but forgets a box she was supposed to deliver. The box and the portrait will soon pull Jill deeper into the mystery.

Jill is discovered dead in Tim's flat, wearing the pink dress. The portrait’s face has been erased and the photo it was based on has disappeared. The police open a box to find an empty Chianti bottle labeled Nightingale & Son, a firm that does not exist; the bottle is also sketched on a Rome postcard Tim received.

With Jill's murder and the missing artwork, Tim becomes a prime suspect. Police scrutinize his alibi as the investigation widens. Clues increasingly point to a broader international diamond-smuggling scheme.

Alison Ford is found alive and seen wandering around London. She appears at Tim's door to explain that the woman killed in the crash was not her. She mentions that Lewis warned of an international diamond-smuggling ring and that Alison's father was involved. She fears the truth may remain buried unless they act.

Alison clarifies more about the diamond-smuggling ring and why the missing hitchhiker could be a key victim. She implies several major characters are connected to the thefts and that her father fears exposure. The revelations recast the deaths as pieces of a larger conspiracy.

Alison leaves Tim and goes to see her father in a hotel to extract the truth; he plans to flee the country. She phones Tim to update him, keeping him in the loop as events unfold. The unfolding investigation ties surviving characters to the smuggling ring and the blackmailer.

Two additional murders and a suicide occur as the mystery deepens. It becomes clear that four of the major characters are linked to the diamond ring, and an independent blackmailer is at work. Authorities close in on the conspirators as arrests follow.

After arrests are made, Tim and Alison are left alone; he asks if she can stay while he completes her portrait. She agrees, indicating a life together born from their dangerous alliance and shared secrets.

Tim promises to finish the portrait over time; Alison replies that this is fine. The two seem committed to each other as the mystery settles around them.