Plot Revealed Below!
Valentine's day, 1958. Charles Hewitt, an eminent H-bomb scientist, is found garroted with cheese wire on the banks of the Thames. His mouth has been stuffed with newspaper, there's lipstick on his neck and strands of blonde hair are found on the shoulder of his jacket.
Hewitt, a confirmed bachelor, lived with his mother, Marie, and sister, Fiona. He received much hate mail relating to his controversial research at Aldermaston, but Fiona has no idea what he was doing on the banks of the Thames on Valentine's night -- there was no woman in his life as far as she knew. Marie utterly disapproved of her son's work and despised what he had become. She is not surprised that he has been murdered.
Meanwhile, photos of Jericho and Juliette have been sent anonymously to Scotland Yard. Cherry warns Jericho that public knowledge of this could be hugely damaging to his career and the force as a whole. Jericho discovers that it was a colleague, Christie, who sent the photos.
Was Hewitt's murder politically motivated? Caldicott infiltrates a local CND group, led by Alex Gadd, and follows them to Aldermaston, where they are planning their next attack. But Caldicott blows the whistle too early and Jericho lets Gadd go.
Caldicott reveals to Harvey that Angela is pregnant and that they have to move the wedding up. Caldicott blames himself.
After the discovery of a second body, Tom Eliot (a postman) murdered through identical means, the trail leads the team to a marriage bureau where both Charles Hewitt and Tom Eliot were members. Jericho is sent on dates with five women who requested information on Hewitt and Eliot. The plan is to take the women out to dinner, get their fingerprints and a print of their lipstick (the lipstick on Hewitt's neck has been identified) to try to link them with the crime scenes.
Of the five women, two -- Margaret Epsom and Sadie Swettenham -- don't have alibis for the nights in question. Margaret is a fearsome blonde who recently divorced her philandering husband. Sadie, a brunette, is a widow with two small children who moved to London to find work as a nurse. Jericho is charmed by Sadie, and she ends up spending the night with him at his flat -- although she takes the bed and he sleeps in a chair.
Caldicott has found a pattern in Hewitt's hate mail -- the majority seem to be from a person who is dyslexic. Fiona still claims she doesn't know who they could be from. Marie reveals that at some point on the night he was murdered, Hewitt returned to the house -- she heard him enter his room.
Jericho instinctively doesn't believe that Sadie is capable of the murders, and believes Margaret to be a much more likely suspect. But when he interviews Sadie, Jericho discovers that all her stories have been lies. She lives in a rundown studio apartment, not a lovely big house. Her son Edmund, who has a terrible stutter, reveals they've only been in London for three weeks, not a year as Sadie had claimed. Sadie says she only wanted to present the best version of herself. And Jericho is the only man she's met through the bureau -- she applied for the details of other men but decided not to meet them.
Margaret Epsom reveals she did go on a date with Eliot and she found him utterly repellent. But when she went on a date with Hewitt they had been followed by a young man carrying a red tote bag.
Caldicott has followed Fiona Hewitt to the Hall where the CND group meet. She had been having an affair with Gadd but had no idea that he had been the one to send all this hate mail to her brother. She believes that Gadd murdered her brother.
Caldicott follows Gadd, who is carrying a red tote bag, to the home of another scientist. Jericho believes Gadd is carrying a bomb. Before the bomb disposal team arrive Caldicott talks Gadd into handing the bag over to him.
Gadd admits to following Hewitt the night he died -- he had wanted to kill him but lost his nerve. When shown photos of Margaret and Sadie he only recognizes Margaret -- not Sadie. Jericho is relieved.
Tensions between the team are growing. Harvey believes that Sadie is their only suspect. Jericho sends Caldicott down to Coventry, where Sadie previously lived, to find Hughie Bremner, Sadie's last partner who mysteriously left her.
Caldicott discovers she was known as the 'Black Widow.' She would take in lodgers and had a reputation for getting into relationships with them, before they moved on -- it's how she got her kids. She changed her appearance for each man: style of clothes, hair, hobbies, to find a way to please them. When Jericho still denies that she could be the killer, Harvey loses his temper and accuses Jericho of having lost his judgment.
Jericho picks Sadie up at her flat to take her dancing. He finds 'Pink Beach' lipstick and a blonde wig among her things. Hughie Bremner's body is found by a canal in Coventry; he too had been strangled with wire.
Sadie's arrested and Jericho's taken off the case -- how could he have got it so wrong? Sadie admits that she went on a date with Hewitt on Valentine's night -- but she didn't kill him.
Louis has some news for Jericho -- he has found Hewitt's watch that was missing from the crime scene -- and the kid who sold it had a stammer. It's Sadie's son, Edmund, who is the killer! Jericho warns Harvey who says he's getting the kids picked up.
Returning to his flat he finds a letter from Juliette -- she's decided to leave as she realizes that her presence is making Jericho's life very difficult. From out of the shadows Edmund attacks Jericho with a piece of cheese wire. Jericho wrestles him to the ground where he begins to weep -- his mum had been so hurt by men in the past and he just wanted to protect her.