Having abandoned his collar, Sidney has stepped onto the road to perdition. Rain soaks him, his Bible is drenched, a young man spits at him, and dogs threaten him as he journeys north to a crossroads. He is met there by Ronnie, Mrs. Maguire’s thieving husband, and is led into the ragtag gypsy encampment Ronnie calls home. Sidney has tracked Ronnie down to retrieve Mrs. Maguire’s money. But Ronnie convinces him to stay through the evening, when there is an engagement party. Then he’ll hand over the cash.
Unfortunately, a posh vicar is not entirely welcome among the Romany. Their leader, Pal, is suspicious of Sidney, as is his soon-to-be son-in-law Abraham. There’s also some tension between Abraham and Ronnie, while Abraham’s fiancée Luella seems less than excited about her marriage. And she’s upset about the Romany plan to move on soon, leaving behind a beloved spot. In short, the camp is full of internecine conflict waiting to explode.
At the party, Sidney strays further from righteousness by flirting and dancing with a confident gypsy woman. Ronnie makes a toast, revealing in the process that he is married, in spite of his continuing marriage to Mrs. Maguire, and has kids with his new wife Cora. Sidney confronts him about his bigamy. Later in the night, Sidney sees Abraham run from the barn looking for Luella. Next thing we know, Ronnie is found dead in front of his wagon.
Pal blames Sidney; Sidney suspects Pal. A fight breaks out between them, stopped only by Cora’s cry that Mrs. Maguire’s money is gone.
Back in Grantchester, Leonard has told everyone that Sidney is taking a holiday at the beach. After Cathy packs a suitcase for Geordie and kicks him out of the house, he gets the truth out of Leonard and leaves to fetch Sidney. He finds him at a phone booth, calling the police about the murder. Geordie scolds Sidney for abandoning the people who need him: Amanda, Leonard, and implicitly Geordie himself. But Sidney believes that they’re all better off without him. He sends Geordie to tell Mrs. Maguire about Ronnie’s death and second wife.
Sidney returns to camp to find that Pal has dismissed the policeman with a story that Ronnie fell. The vicar goes to talk to Cora while she burns Ronnie’s possessions. She had no idea her husband had a living wife; she only found out at the party, when someone overheard Sidney confront Ronnie. Sidney also realizes that she has cancer. He had seen a radiation treatment pamphlet in the wagon, and now concludes that Ronnie stole the money for her. His lie about cancer was based in truth.
Sidney wants to talk to Luella, but she has disappeared. He, Pal, and Abraham go in search and find her at a nearby forge with another man, Marcus. Abraham is furious and Luella blurts out that she wants to marry Marcus, not Abraham, and live a settled life. Sidney discovers the stolen money in her purse. She confesses that Ronnie knew about her affair with Marcus and had been lying about her absences to cover her back. The night he died, he was planning on telling Pal about Marcus; he told Luella he had money she could use to run if Pal flew off the handle. When she found Ronnie dead, she panicked and took the cash.
That means that whoever murdered Ronnie didn’t do it for the money. Sidney realizes who the culprit is, and goes to find him at the forge. Abraham is there, pointing a gun at Marcus. He accidentally killed Ronnie by lashing out at him with a poker after Ronnie refused to tell him where Luella kept going. Abraham was set to take over from Pal as leader, but he’s always felt weak and pathetic.
Back at the camp, Mrs. Maguire has arrived, having forced Geordie to bring her. She insists that Cora return her money; neither woman likes each other. But after Luella gives the money back to Cora, Cora hands it over to Mrs. Maguire, who then returns half so that Cora can get cancer treatment.
Mrs. Maguire returns home and finally takes off her wedding ring. She’s free. Geordie goes to see Margaret to end things once and for all – he’s got a marriage to fix. And they all live happily ever after… until Sidney comes back to Grantchester and goes to Amanda. Disappointed by his disappearance, she issues an ultimatum: her, or the church.