Despite having had sex with her exactly once, Grantchester begins with Will lying on the floor of the church, declaring his undying love for Maya and begging God to tell him what to do. It's very Will, as is meeting her in secret to tell her it will never work only to take her home and sleep with her again, and then grabbing her to make out in an empty precinct office. The juxtaposition with the Carmichael's Cleaning Supplies ad is hilarious and timely, as we cut from Geordie with a pillow over his ears to Cathy watching the ad, shown by Melanie Carmichael (Kirsty Besterman). Swinniton's is pushing its products. Cathy's not pleased with being forced to work for Carmichaels unpaid; Clive (Ryan Early) sweet talks her into being quiet.
Leonard: She thinks she's breaking a commandment when she steps on an ant.
It all comes full circle when Geordie's next case turns out to be the death of none other than Lester Carmichael, owner of Carmichael's cleaning goods brand. They're greeted by Melanie, scrubbing blood off the front step and insists she has no idea why there was a 999 call, claiming the blood came from her husband cutting himself. The two are the couple from the commercial; Lester's death is due to a pellet to the artery in his neck, which shifted and bled out when he laid down. Like last week, Wallace does not understand why Will is at the autopsy, and his "just saying a prayer" schtick is starting to wear thin, but he sits in on Melanie's interview anyway.
The pellet comes from a toy guy, but the kids in the commercials are not theirs; they have none. However, Lester was embezzling, and Melanie knew it. She claims she was at Swinniton's when Lester called, which means Geordie has to question Cathy and her coworkers. It goes about as well as you expect, with Geordie going full caveman about her friendship with Clive while Will learns Melanie received a call and left in a hurry. The call wasn't from her husband but Betty Rose (Rebecca Lacey), a madame. There's also a boy in the yard dressed as a cowboy, the son of one of her girls, Velma (Boadicea Ricketts). Velma's client Douglas Rickman (David Boyle) notably protests his innocence during the mass arrest that follows.
The story adds up pretty quickly: Lester was having an aftercare drink with Betty, post-spanking session, when the glass suddenly broke, and the shattered glass cut his hand. He fainted, and Betty had Melanie come to fetch him. Someone fired the kid's pellet gun, hitting the glass and his neck. (It wasn't the kid, Betty sends him on errands when his mom has clients.) But the fingerprints aren't Betty's on the glass; they are Velma's, whose prints are on file from her previous arrest for threatening her abusive boyfriend. She was the one in the room and his BDSM mistress; however, she claims Lester promised to make her his kept woman, and she believed he was serious.
Cathy's work schedule and her inability to trust Geordie to step up have led her to ask her niece, Bonnie (Charlotte Ritchie), to come to stay with them. A widow with a small but serious son, Ernie (Isaac Highams), she's the kind of energy the household needs, even if Will is slightly shocked by her. When Geordie claims he can handle the kids to Cathy, she has Bonnie bring them round to his office while she goes on a work "thing" with Clive to the pub. Bonnie admits to Will she doesn't like Clive either, and the two leave Geordie to his children as he offers a tour of Grantchester. They have a heart-to-heart over his and Geordie and Cathy's relationship problems, and Will realizes they're really hitting it off as friends.
Last week there was a brief moment when Jack noted Mrs. C was sleeping at the vicarage and asked her to come home, and she made an excuse about the summer heat. That has now blown up into Jack suspecting an affair; something Leonard finds preposterous. But her diary has her seeing a "DW" when she claims to be at bingo. It is obviously going to be a "Doctor W____," but we'll let Grantchester pretend otherwise so Leonard can sneak about and then learn dramatically that Mrs. C is secretly ill. He goes with her and holds her hand like the good son he is as the specialist, Dr. Ford (Henry Everett), tells her she has uterine cancer and will need radiation and a hysterectomy.
On his way to take the kids home, Geordie sends Miss Scott to the pub "to have a drink," aka check up on Cathy. Geordie shouldn't have worried, Clive's already screwed everything up, and Cathy tells him to bugger off. Miss Scott sits down in his place, introduces herself as Jennifer, and tells Cathy that going sapphic is just as problematic as being straight. Cathy realizes Geordie sent Miss Scott to spy on him, but she offers to buy the rounds using his money, and the two get drunk. When Geordie gets into the office the next day, he finds Cathy there. She and Miss Scott team up to demand two-hour lunch breaks to hang out regularly, and Geordie can do nothing but nod.
While Will may have found a girl worth his time and attention, he's not yet bright enough to see it. Instead, he goes home to think. Will finds Sidney's old box of vinyl and goes full OG Hot Vicar on the couch listening to jazz before Maya comes round and falls into bed with Will again. But by the next day, Will has realized he does need to break this off, deciding he's not actually in love with Maya, just infatuated with the fantasy of it, and he can't live in a false reality. He leaves her, thank heavens. Hopefully, he's learned his lesson about trying to be Sidney.
However, Geordie's remark about women conspiring helps him hit upon the key to the mystery. Miss Scott notes a witness saw Melanie bring Lester home, with Betty helping. But those two are not guilty of anything but protecting their businesses. Velma isn't guilty either; she bought the fantasy that Lester would take care of her. The jealous person was Douglas, Velma's other client, who couldn't handle seeing her with another man. Though she's not guilty of murder, Betty Rose is going to jail for her brothel, but not before leaving all her cash to Velma and her son to live a better life.