Grantchester began this season with one of its heaviest storylines to date, Leonard's sexuality coming out in public. This being 1958, being gay is illegal, and it led to him being put in prison two episodes ago. Last week spent time focused on Will and the parish moving on, Will trying to find the nerve to visit, Henry Jones hired as the new curate. But this week, the series stops sidelining Leonard and treating his and Daniel's trauma like a fulcrum for other people's growth, with an opening that focuses directly on Leonard's ongoing experience in prison as Daniel dives into the bottom of a bottle.
Henry: Your Freudian nightmare of a sibling is disrobing in the parlor.
Leonard, as one can imagine, is not having an easy time. His cellmate, Joe Davies (Bobby Lockwood), is a violent bully who amuses himself by beating up his gentle companion. He's befriended by another gay man, Elroy Hastings (James Bailey), an upper-class guy who cheerfully treats his time inside as a laugh and claims that Joe (who beats him up regularly) isn't such a nasty guy. But Leonard's real comfort is retreating to the church that rejected him, visiting with the Chaplin, Rev. Nick Byatt (Paul Ryan), who relentlessly pushes him back into the closet.
Daniel's not the only one who's been drinking. Johnny has been taking Geordie out all night, keeping him at the pub until closing time. Will is too, though at least he has the excuse he's been saddled with Tamara, who Amelia chucked out for misbehaving. (Henry is as appalled as Mrs. C., though not for the same reasons.) But at least he's keeping up the visits with Leonard and meeting those who have loved ones on the inside, including Joe's father Arthur (Ian Burfield) and Elroy's mother Sophie (Gabrielle Glaister). Despite it being Joe who acts out on the inside, Elroy acts out at visiting time.
But perhaps there's a reason, as a few hours later, Elroy is deceased. Joe is dragged away, protesting his innocence. The prison governor, James Milton (John Bowler), believes he has their man, as Elroy's death was by drowning in a tub, the same crime Joe committed. (He murdered his mother in the bath.) For Leonard, it should be a relief, now that his tormentor is gone. But Leonard was always the open-hearted sort, and he believes Joe, even if Milton sneers at his protestations. He calls in the calvary, triggering Geordie, whose memories of imprisonment in Burma come flooding back at seeing Joe in solitary. And it's not long before this episode becomes Grantchester: Leonard Finch Investigates.
This is not the first time the series has turned to Leonard as the series detective. As part of the changeover from Sidney to Will in Season 4, the season did an episode where Geordie teamed up with Leonard to solve a crime. It was a good adventure in that it demonstrated Geordie's odd couple pairings could only go so far while allowing Leonard some front and center action. It was also a fan favorite that season; it's not surprising that to centralize Leonard's story once more, it's his turn to wear the deerstalker hat.
Leonard explores where Elroy died and discovers the box he was working on in the woodworking space, labeled "Veritas." When Sophie turns up, asking for help, he sends her to Will. She reveals that she doesn't believe Joe did it, that someone had come to the house trying to blackmail her into paying protection money to secure Elroy's safety. She refused, hence Elroy's freak out when she visited. Will realizes that Daniel's drunken rage he witnessed was at someone threatening the same thing, but with Leonard. He's not wrong, as the man, Lynch (Cameron Jack), turns up in Leonard's cell as the night guard and begins beating Leonard up. But before he gets too far, Will and Geordie turn up, Chaplin in tow.
Lynch admits to roughing up Elroy but insists he left him alive. But it's enough to get Joe out of confinement for the moment. However, the sight of Joe's collapse in the face of his punishment is too much for Geordie to handle, as is Will's continuing insistence that Joe's original murder charge against his mother doesn't add up. But this is Leonard's case, which means Will wanders off to get the B plot of planning a surprise anniversary party for the Keatings. It's all a bit uncomfortable with Mrs. C. discovering the seminal book, The Second Sex, and Tamara spiking the punch. It's a good idea, but Geordie's drinking with Johnny means he turns up late and smashed, embarrassing Cathy and upsetting Esme.
Meanwhile, Leonard solves the box's mystery; it's got the code to the safe in the Chaplin's office inscribed on it. Inside there's a book with all their information. The Chaplin was the brains behind Leonard's muscle. When the Chaplin catches him, he pretends Leonard hit him and dragged him off to solitary. After all, who's word are the guards going to believe? But the Chaplin doesn't count on Will and Geordie putting together that Joe took the blame for his father killing his mother, that the murder was never his, and that this meant the killing of Elroy was a set up by someone who had heard Joe recite the details.
With the Chaplin arrested and Leonard released, he takes over the Sunday prayers and communion in prison. It's the thing he needed, and by episode's end, it's clear this is what's going to help him get through. But Geordie may not. Despite his words to Leonard that holding on to prison and the memories of incarceration keep one locked away long after they've gotten out, Geordie's still holding on. The list of those who died beside him in Burma, he keeps with him, tucked into his hatband.