Grantchester Season 5 continues with a theme, once again opening with Will on his motorbike. He's meeting Mum's boyfriend, St John Gurney-Clifford (Dominic Mafham). The good news is St John doesn't openly sneer at Will's chosen profession. Instead, he's faintly amused by it, which is rather worse, all things considered. Almost as bad as finding out St John is rushing to get Amelia to the altar.
Will heads back to take it out on the punching bag, hard enough that even Vic feels the need to ask what's wrong. Meanwhile, Geordie is already regretting inviting Cathy's mum Diana to stay, and Cathy is not exactly sympathetic.
Geordie: "There's only one thing that makes a person look more guilty than running away, and that's running away with bags."
Will and Leonard head out for a walk with Dickens. Will is grumping about his mother's life choices, while Leonard frets over Mrs. C's disapproval of getting a television. But both are pulled out of their troubles abruptly when a car comes roaring around the corner and proceeds to take out a gentleman carrying orchids. Will is sadly useless as a witness when Geordie arrives, having not caught anything, not driver, not car make and model. Larry gets an identity for the victim: Dickie Astor, a financier. He spills it to Ellie as well when she shows up at the station. Apparently, someone other than Will has a crush on our journalist.
Larry also turns up next of kin, Jacqueline Astor (Caroline Martin), who insists her husband didn't bring her flowers anymore. She's pretty broken up, telling Will she'd been with him since she was 19. Geordie notes Dickie may have a thing for the younger women, as Astor's overly-familiar secretary Rosalind Reece (Molly Jackson-Shaw), looks like she's barely out of grammar school. Will manages to recall the plate number, which is registered to Elliot House. Unfortunately, Will is still a neighborhood newbie, so they round up Mrs. C to help with the local knowledge of where that is, even if she refuses to go with them.
The house looks like something out of a haunted story with overgrown grounds and a dilapidated air. No one answers the door, but it's not locked, so Geordie and Will let themselves in, at which point two older men appear out of the darkness. They are Harry Graham (Matthew Marsh) and his brother John (David Bamber), the latter of whom is ordered back to his room by Harry. Harry insists he's barely driven the car in 20 years and this is all a mistake — until they go to the garage and see the damage from the accident.
The Grahams are not a client of Dickie; they're distant relations. "Not distant enough," Harry bites off before launching into a near tirade that Astor ran Ponzi schemes, and only gullible fools gave him their money. But the ledger shows the Grahams were substantial investors, and the "damned fool" was John. Harry is livid Astor bled his brother dry, giving him quite the motive. Will heads back to talk to John, believing Harry abused him, only to find Ellie's followed him there. They find a gorgeously tended garden -- and John walking with Jacqueline. As Mrs. Astor leaves, Will approaches John, whose anxiety seizes him up. Ellie starts asking about the flowers, and in no time, John's opened up, bringing out a giant bouquet of white orchids.
Luckily, Jacqueline is more forthcoming. She confirms her husband treated the Grahams abominably, and she was trying to make up for it. She also admits she didn't love Dickie anymore, once the romance and flowers faded, it was over. Geordie recognizes John's symptoms: shell shock. Harry's not abusing John; he's protecting him. The bluster is because he's terrified it was John. When Will and Geordie question John, he admits he hated Dickie -- put for picked the orchids, which he didn't deserve. He agrees with Geordie he "ran the bastard down." Will's not sure he believes John, who isn't entirely in his right mind. And there's a question of why Dickie picked the flowers. As Larry says, the flowers indicate a crime of passion.
But they weren't for the wife, Jacqueline says the flowers were only at the beginning of their courtship, and that was long over. Realizing they were for Rosalind, Will and Geordie head back to Astor's office, where she proceeds to run. But though Rosalind has the swindled cash from the Grahams, she didn't run Astor over. She can't drive. Also, Rosalind wholeheartedly believes Astor got the money legally, claiming he was leaving his wife for her. But when she burbles, he was supposed to tell Jacqueline, Geordie and Will realize they've cornered the wrong woman.
But Jacqueline surprises them. It turns out she was planning to leave Harry and John was helping her, lending her the car. On the way out of town, Jacqueline saw him in the street with the flowers and came at him thinking to scare him. When she saw his face, her whole life wasted upon a sad old man, and the bouquet, she realized he was going to do it all again. She couldn't stop herself and ran him down.
God bless Leonard. He bought the TV so he could watch Eurovision. And for all Mrs. C's complaining, the moment the picture came in she was entranced, ruining Leonard's hopes of some peace. It's not clear if he was hoping to sneak Daniel over to watch, but he's planning on it the next afternoon for the Grand Final as he convinces Mrs. C to head out of the night. (For all the French food, The Netherlands won in 1957.) Daniel spends the night, and Leonard tries desperately to act like he can handle himself as an adult over this. But that all comes crashing down when Mrs. C. arrives back early the next morning. At least Will is willing to be the distraction to help get Daniel out the door.
Also, for all Geordie complains about his morning routines thrown off by another adult, Diana's presence may be better than anyone hoped. She's now playing wife to both him and Cathy, who has gotten promoted to Shop Stewart for Ladies Wear at Swinnerton's. Though maybe not. Diana likes playing wife to Geordie, but not so much her own daughter. She's also bought into the whole idea of unions as a hotbed of communism, and is appalled by her daughter's job, sneering her daughter works for pin-money and is a disappointment as a woman. But Geordie is fine with her there, and happy with Cathy working, as long as the spam fritters keep coming...