Season 08 Episode 05

Will is at his most energetic and least stable. He preaches against the danger of refusing to move on from the past, types a letter to a newspaper editor urging readers to protest against nuclear arms, and leads a scout troop in song. Mrs Chapman, who takes this for a recovery, is now more worried about Leonard. Two men were admitted to Addenbrooke's the previous night after a suspected poisoning; one died, the other is in a serious condition. The dead man is Dr Bill Lambert, and the survivor is Mike Cotton, the barman who served him at the Week End Club.

Geordie has been put on desk duty clearing the archives, and DCI Elliott Wallace assigns the case to Larry Peters. Larry goes to the hospital to speak to Mike's wife, Anna Cotton, and learns that Lambert was their family doctor. At the club the barmaid, Sharon Anderson, says Mike served the doctor personally, that she heard someone giving the owner an earful just before the collapse, and that she cannot say which glasses were theirs. Bernie Palmer, the owner, says Lambert had asked for a special reserve cognac salvaged from a German U-boat, which is kept locked in his office and has been drunk from before without harm. Larry takes the bottle and the uncleaned glasses and closes the club, refusing Palmer's attempt to square it with him.

Larry searches Lambert's surgery and finds a woman going through the drawers, and a notebook in a form of code. The woman is Debbie Stephens, Lambert's niece, who worked for him for about a year and was recovering two months of unpaid wages. She denies the poisoning, says her husband is bedridden and that she was at home, and the laboratory finds cyanide in the special reserve bottle and traces in two of the glasses. Larry questions Palmer, who says he gave the barmaid the key to his office. Sharon says she fetched the bottle only because Mike was busy, and that none of the women would serve Lambert when he had been drinking. Mike wakes and tells Larry that Lambert always drank alone, that people disliked him, and that Lambert had asked him to share a glass of the special reserve, and that Lambert drank far more of it than he did.

Miss Scott accompanies Larry to the hospital and recognises Mike's accent as Russian. Anna Cotton emigrated in 1956 under the name Alina Papp and married Mikhail Kurakin, now Mike Cotton. They met in Hungary, where Anna was a university professor who led protests against Soviet policy and was blamed for the deaths of some of her students during the 1956 uprising, and they fled and changed their names in England for safety. Miss Scott breaks the code in the notebook, which is an account of payments listed by initials, and there are two hands in it, one of which matches Debbie's. Debbie admits Lambert was blackmailing patients with what he learned while treating them, including Palmer over an affair that Lambert had treated, since Lambert had threatened to tell Palmer's wife if he was not given free drinks. Palmer says he had had enough and that this is what the argument was about, and that if he had poisoned Lambert he would have been clever enough to dispose of the evidence.

Geordie and Will work the case alongside Larry despite Wallace's attempt to keep Geordie out of the way by assigning him a job hours away. Miss Scott finds that the first set of initials in the ledger, A.P., first appears the week after Lambert saw Anna Cotton, on her first and only visit to him. Geordie forms the view that Mike poisoned the bottle on his wife's behalf, and Will is sceptical, since Mike would not have known the dose.

Anna Cotton killed Lambert. Lambert had worked out who she was and told her he knew people at the Russian embassy, which would have ended the life they had built in England. She went to the club and asked Mike to show her the special reserve bottle before Lambert's usual arrival, and put cyanide in it. She had been a chemistry professor, so she knew the quantity, and she had intended Lambert to be the only person drinking from it. That night Lambert asked Mike to join him in a glass. Anna admits the killing and is taken to the cells, and she and Mike are allowed a moment together first. Will asks her whether the guilt ever goes away, and she says it never does, and Geordie tells Will he is nothing like Anna and asks him to step away from the case for a while.

Leonard, in the same episode, has invited a local councillor, Miss Taylor, to the halfway house to reassure her about it, and Will has told Mrs Chapman to pose as the housekeeper and Jack to pose as a new resident. Keith speaks about his drinking and the value of the house. Miss Taylor is engaged by it, but Will, energised by pills, attacks her for offering false hope she does not intend to deliver, and she leaves. Geordie takes the pill bottle from Will in his office and tells him to try harder. Cathy tells Geordie about her promotion and about Elliott's treatment of him, they agree that whether he retires has to work for both of them, and Geordie types a letter of resignation. Mrs Chapman sees Daniel laughing with another man on his doorstep and reports it to Leonard as a new relationship, and Leonard confronts Daniel, who is angry that this was the only reason Leonard had come to see him. Leonard, still raw, tells Will he is no use to anyone while he only wallows in self-pity and that he will never trust him to do anything for him again. It is Ernie's birthday, and Will does not come, and Geordie goes looking for him and finds a note about leaving.

The case is solved by a ledger of initials opened at the letter A, which is as close as the series comes to a clerical clue deciding a murder, and by a woman who was a chemistry professor in Hungary being the only person in the episode who could dose a bottle precisely. The accident is the reason the episode's structure works, because the man investigating the poisoning is the man swallowing pills, and the confrontation with Miss Taylor is the first time anyone in the series says out loud that Will is not fit to be doing this.