Simon LackPaul Temple and the Alex Affair, aired in 1968, was the last Paul Temple radio mystery for 30 years.
Part 1A conductor collecting tickets on a train finds a woman dead. He enlists a passenger, Mr. Wilfred Davis, a Welshman, to verify. On the window is scrawled the word, Alex.
Sir Graham Forbes and Inspector Crain visit Paul Temple to ask him to look into it. Paul refuses - he's started a new book and he's promised Steve not to get mixed up in any more murders. He does ask Sir Graham to give him the history of the Alex murders - this is the second one - and Forbes mentions that both victims had, written in their diaries, the name "Mrs. Trevelyan."
He goes to Broadcasting House, driven by Steve, to take part in a Question Time show. One of the other guests dies, but before doing so whispers to Temple the name, Alex. Steve is driving home with Paul when a car tries to force them off the road. They both get the number, and Steve releases Paul from his promise.
Paul and Steve wait in a bar for Spider Williams, an acquaintance of Paul's. He's tracked down the number - the car belonged to a Doctor Kohima. (At the same time, he is greeted by Wilfred Davis, who mistakes him for a man named Simon Phipps.)
The next day Paul visits Dr. Kohima, while Steve has come with him to go to a registry office to find a new valet, as their old one, Charlie, is in the hospital. In Dr. Kohima's waiting room, he meets Carl Lathom (Simon Lack). Lathom is there early for his own appointment with the Doctor. A playwright - the actress Norma Rice who had been found in the railway carriage had been in his one and only play - He tells Paul that he's been suffering from hallucinations - a woman dressed all in brown following him - but that Dr. Kohima had cured him.
The secretary comes in and tells Paul that Dr. Kohima (a nerve specialist) will see him in a moment, and tells Lathom that he's early. Lathom says he was in the area with nothing to do, so decided to come in and wait. The secretary goes back to her sanctum and Lathom tells Paul that her name is Mrs. Trevelyan.
Part 2Paul goes in to Dr. Kohima, and tells him Kohima that his car had been used to try to run them off the road the night before. Kohima says his car has been in a garage for repairs for several days, and asks Paul to call the garage to verify. Paul does so, and learns the car had been ready the night before, and that it had been taken out for a few hours by Kohima's chauffeur. Kohima denies having a chauffeur.
Part 3Part 4Part 5Part 6Part 7Part 8Carl Lathom is revealed as Alex. He pulls a gun and hold the others at bay, but valet Ricki hits him on the head with a vase, saving the day.