Geordie: This is your life. It's an endless merry-go-round: Sin, feel bad, drink; sin, feel bad, drink.
Having rededicated himself to church life, Season 4's premiere marks the first day of the rest of Sidney Chamber's life. Sermons on Sunday, Church upkeep on Tuesdays, Jazz records on Fridays, with criminal busting thrown in to break up the monotony. But that all changes when Sidney heads to hear a talk on "Religion's Role in the Civil Rights Movement." There, he and Leonard (Al Weaver) run into Will Davenport, Chambers' replacement as the new Chaplain of Corpus Christi. But Sidney's attention isn't caught by Davenport, or American Civil Rights advocate Rev. Nathaniel Todd (Paterson Joseph), but rather his daughter, Violet Todd (Simona Brown).
Having African-Americans speak about race doesn't go over in Grantchester any better than it does in Alabama, where the Todds hail from. Though American audiences usually think of us as the country with a race problem, the U.K. has always had issues as well. The riot that breaks out during Todd's speech may be driven by fireworks, not gunfire. But the chaos is terrifying, especially when Todd's son Charles (Tok Stephen) winds up fatally stabbed. bringing in DI Geordie Keating (Robson Green) to investigate.
The Todds have been receiving threatening letters from The Phineas Society, most of which are aimed at Violet. Turns out they are from Gregory Jones (Dominic Herman-Day), who made the group up in order to impress girls. (He set off the fireworks too.) But when someone breaks into the house where the Todds are staying, Chambers moves them bag and baggage into the vicarage, giving him and Violet a chance for a heart to heart over the nature of prejudice. The chemistry between them is as fantastic as Brown's "American Southern" accent is painful, and leaves little doubt as to how Sidney will be tempted away from the church for good.
Davenport turns up with the murder weapon, saying it was given to him in confidence. Geordie drags him in for questioning, in what feels like a screentest-esque scene for casting Norton's replacement. The rat-a-tat-tat between Green and Brittney should put to rest any concerns about the coming cast change; the two are great together. So are Norton and Brittney in the scene that follows in which Chambers convinces Davenport to confess that it was Robert Deveaux (Antony Acheampong), the other member of Todd's entourage, who gave him the knife. Deveaux admits he staged the break-in to scare the Todds into going home. But he didn't kill Violet's brother; he was hoping to marry her. So who set Robert up? Turns out it was Professor Henry Barkley (Samuel West), who went into a jealous rage when he saw Charles dancing with his wife.
As this premiere aired in the U.K. as two separate episodes, the mystery is over with half an episode to go. The Todds have gone, leaving Sidney drowning his sorrows at levels heretofore unseen, as Geordie worries that his chasing down criminals is a redirected suicidal urge. He's not the only one worried, and Mrs. Chapman (Tessa Peake-Jones) and Leonard even attempt to stage an intervention. Meanwhile, Geordie has a new DI moving in, Sean Donovan (Felix Scott), with whom he'll be sharing an office. Ch-ch-ch-ch-changes!
The new case focuses on prostitute Sadie Parker, found dead with Sidney's missing jacket heaped among her bedclothes. Not that Sidney's a suspect, but it would be helpful if Chambers weren't totally blackout drunk at the time. Instead, they check the slum where she lived with flatmates Ava (Holly Aston), Peggy (Kirsty J. Curtis), and Lottie (Sofia Oxenham), and then chase down her pimp. He's Rupert Simpson (Nicholas Rowe), an upper-class twit playing golf with the head of the Council, Archer Davis (Patrick Baladi). Not that it stops Chambers from blowing up at Simpson, much to Geordie's alarm. Geordie winds up investigating alone, facing down the man managing Simpson's cadre of girls, Rory Dale (Diarmaid Murtagh).
But Sidney's working too. Turns out, Violet hasn't left the country yet. When she and Sidney run into each other on a crowded street, it's obviously a matter of time before he chucks it all for her. He talks through the half-remembered evening with Sadie, to which Violet delivers the best "you're a self-centered, wallowing idiot" lecture at him for not helping the girls who still live. Meanwhile, Geordie's investigation reveals that Simpson doesn't own the club, but he can't get an answer as to who does, and his insinuation the girls might talk has brought Dale down upon them, just as Violet and Sidney head over to save a soul or two. Violet might not have meant "saving" so literally, but she's as brave as Chambers in taking the men on and driving them out.
She inspires Sidney to get back on the case with Geordie. The visit to Simpson's office is revealing as there's a photo of every girl posed with Councillor Davis. Davis owns the club and the slums and is planning to sell the latter to the Council. But before Geordie can crack Davis, Dale walks in and confesses to being the mastermind and killing Sadie too. Obviously, he didn't do it, he's just being paid to take the fall. Sadie was murdered by Ava, who panicked when she saw Sadie confront Davis in front of his council buddies and killed her out of fear that it would all come down on their heads. At Sadie's makeshift funeral, Violet's words about changing their lives and fortunes, and Sidney's encouragement convince the remaining girls to stand up and bring Davis down.
Despite Sidney's begging, Violet won't stay in the U.K.. Her fight and her world are back home in Alabama. So what does he do? Chambers announces he's packing up and going with her instead. This isn't going to be like Amanda, though. There are no backies this time. Leonard and Mrs. Chambers beg Geordie to talk him out of it, but Sidney is determined to change his life and fortunes too. At least there's time for one last game of backgammon before he goes.