It is 1953 and just outside the Cambridgeshire village of Grantchester, local vicar Sidney Chambers has lost track of time, having spent a lovely morning with his friend, and with whom he is secretly in love with, Amanda Kendall. He races to the church, Sidney arrives just in time to minister the funeral of a local solicitor. Sidney does his best to comfort a young German widow Hildegard Staunton but he is soon called away from his duties when Pamela Morton asks to draw Sidney into confidence. She reveals that she was having an affair with the late solicitor. She believes did not commit suicide but was in fact murdered.

Sidney is unable to say no after he is pressured by his sister Jen into attending Amanda’s engagement dinner. As Sidney attempts to deal with the evening by having too many drinks, old tensions run high between the school friends of Amanda and Jen. After Amanda’s engagement ring goes missing, Jen’s boyfriend Johnny is accused of stealing it. The following morning, one of the guests at the dinner party is found dead.

Guy and Amanda ask Sidney to perform their wedding ceremony and the upset vicar hits the bottle. After Mrs Maguire points out he is failing in his duties he decides to take a break from drinking and assisting in criminal investigations. Sidney helps Leonard as he moves into the vicarage, and assists parishioner Isabel as she gets ready for her upcoming wedding to new man in town called Arthur. After Daisy is found dead, her mother calls in Geordie to investigate. Sidney ends up being reluctantly being dragged into the investigation.

A fire in the village leads Sidney to another investigation. Meanwhile, a family crisis causes Geordie to become distracted and detached from his job.

After Sidney takes Geordie to Johnny Johnson’s London jazz club, they’re supposed to be leaving their worries behind them in Grantchester. After Amanda shows up unexpectedly, the night takes a rather different turn. Johnny’s sister is murdered, leaving everybody devastated. Johnny and Claudette’s father calls in his friend DCI Jacob Williams to work on the case.

Amanda and Guy’s wedding is fast approaching, and Sidney's betrayal of Hildegard is still in his mind. Those closest to Sidney find it hard to get through to him. The murder of a local policeman doesn’t improve things, as Sidney allows himself to be pulled into another investigation rather than putting his house in order.