Season 06 Episode 06

Rachel Bromilow, who leads the student Campaign for Nuclear Disarmament group at a Cambridge college, falls from the roof of a college building during a night protest in which the group has painted a peace symbol on the wall. Will and Geordie are in the street when it happens. Rachel is found in a pool of blood and dies. Bernard Allison, the college porter, says he disturbed two or three people on the roof and heard her scream. It was a women's college, but he could not tell who they were.

The students close ranks. Rachel's boyfriend Rory St Clair says he was at the debating society and would have stopped her if he had known what she was planning. Her roommate, Petra Neumann, admits she was on the roof with her, that they finished painting and were disturbed by the porter, and that they ran in opposite directions. Geordie finds a letter from the Home Office offering Rachel a post in the International Trade Department. The post-mortem establishes that she was stabbed in the back with a small instrument before she fell, and that the wound pierced her heart so she would have bled to death within seconds.

The group meets to choose a new leader. Rory is nominated and elected, and Petra is nominated and nobody supports her. Will attends as an observer and talks to Petra afterwards, and she talks about Dresden, where she grew up and saw civilians killed. He also learns that Josh, another member, had an interest in Rachel and was seen struggling with her by the stairs. Josh is interviewed and says he drove equipment back to the workshop that night and had run into Geordie in the street before the fall, and he admits he thought Rachel was inviting him up because she liked him.

Painting materials had been stolen from the porter. A screwdriver with blood on it is found in Bernard Allison's toolbox. He says the students put it there, and that they call him a pervert because he once put his arm round Rachel in his office when he found her arguing with Rory. The screwdriver has been cleaned with turpentine, which Will and Geordie take as evidence of a plant, since a framer cleans the handle and leaves the blood on the blade. Petra is searched and a bloodstain is found inside her bag. She admits she cleaned the screwdriver and put it in Allison's van, and admits she lied about Josh, but denies killing Rachel, and Will believes her.

The minutes of the debating society meeting that gave Rory his alibi are then checked. Petra wrote the minutes for both the debating society and the CND group, and the entries are inconsistent. Brought in, Rory is made to read the Home Office letter aloud, and the case against him closes. In flashback, Rachel laughs at him, tells him to stay at home and play the good little wife, and turns away, and he stabs her in the back with the screwdriver and pushes her from the roof. Petra had covered for him to get the leadership back, and he took it. Rory wanted the group's leadership and Rachel was in his way twice over, as its leader and as the woman who had told him she was leaving.

The episode is built as a whodunit among people who will not speak to the police, and the alibi is a piece of clerical work rather than an observation, since the same hand wrote two sets of minutes for the same evening. The screwdriver is a plant that fails because it was cleaned the wrong way round, and the detail of the wound in the back is what rules out a fall during a scuffle. The Dresden account is the episode's best scene and its quietest, and it is what makes Petra credible to Will, which is what puts him back onto the minutes.