The Most Promising Girl of Her Year

Joan Mather (Elizabeth Bell) is a biochemist with a photographic memory, working on a virus project with senior researcher Dr. Bradford (Raymond Young). She reveals to Bradford her worries about the possible misuse of their work with its potential for germ warfare, and that because of these moral problems, she feels she ought to leave the project. Bradford tells her he would be sorry to see her go, but it may not be that easy for her to leave, as Security will want to know why.

Hunter briefs Meres, who is astounded when he sees a feat of Joan’s memory abilities in a recorded interview with her. He realises that she could be potentially dangerous with the amount of information she has. In order to determine where her political allegiance lies, Hunter will ‘give her’ to Callan. However, knowing Callan’s probable unhappiness with the assignment, Hunter tells him that it is his belief that Joan is innocent, and that all Callan need do is prove this.

While Lonely keeps track of Joan, Callan carries out some research of his own on her, and finds that she has a boyfriend who she believes to be a West German biochemist. His name is Karl Donner (David Hargreaves), and he is actually an East German, and in Hunter’s files.

Callan attends a Vivaldi concert at the Royal Festival Hall, also attended by Joan. He approaches her in the interval and they discuss their shared interest in classical music. After the concert, Joan invites Callan back to her flat where he meets Sonia and her latest boyfriend, Toby. Later that night, Lonely, under Callan’s instructions, breaks into the flat and steals a letter. It had been delivered by Horst (Peter Blythe), another East German sent over to arrange to get Joan to Germany.

Callan goes to see Joan the following morning, where he reveals his identity, and the job he has to do to stop Donner. Joan doesn’t believe a word of it, until Meres turns up, followed shortly by Horst, who is quickly overpowered by Meres. Horst is taken to Snell who gets the full details of his mission from him with the help of pentathol, and massive doses of LSD.

In order to convince Joan of the truth, she watches as the drugged Horst admits everything. She is sickened. At Section headquarters, Callan asks the reluctant Joan for her help in trapping Donner, telling her that she is his only chance of staying alive. Back at the flat, they wait for Lonely’s phone call to warn them of Donner’s arrival. However, the phone box outside is broken, and Donner bursts into the flat, gun in hand, taking them by surprise.

Lonely’s call finally comes through, and with the distraction comes an exchange of fire. Joan is caught in the middle, and is killed by a bullet from Callan’s gun.