Sidney receives a series of anonymous phone calls, which he realises may be linked to a series of murders in which the victims were all important community figures killed by someone who leaves dead birds as a grisly calling card. The threat forces Sidney to question whether he can reconcile his relationship with Amanda and his calling as a vicar. Leonard bonds with Hilary as she cares for her dying father, while Geordie's investigation of the killings leads him to a mysterious home for people with disabilities.
After a guilt-induced sermon about desire and duty, Sidney questions himself about Amanda. He wants to resist but soon finds himself in an embrace with her, which is spotted by Leonard who berates Sidney for being such a hypocrite.
Meanwhile, Mrs Maguire is shocked when she is met by a visitor on her morning walk – the face from the past leaves her rattled to the core and she enlists Sidney’s help in dealing with her emotions.
Having left his Grantchester life behind to do some soul searching, vicar Sidney Chambers finds himself heading toward a Romani travellers’ camp in Lincolnshire.
Having tracked down the culprit, Sidney tells himself he is there to retrieve Mrs Maguire’s life savings from the man who stole them but it soon becomes apparent, Sidney is just running from his old life and has no idea what he is going to do.
Seduced by the intoxicating, welcoming community he finds himself in Sidney begins to wonder if he’ll ever return home. But murder is never far from Sidney’s door and when one of the community is killed, Sidney the ‘outsider’ is suspect number one.
On a Sunday morning in Grantchester, Sidney visits the Archdeacon to discuss his resignation. Sidney has lost his faith in a church that won't allow him to be married to the woman he loves. With a heavy heart the Archdeacon tells Sidney he must go away and write a resignation letter in order to make it official. Sidney visits Amanda, revealing his plan. Their moment of joy is cut short when Amanda asks if Sidney has told Mrs Maguire or Leonard… To Sidney's relief, Leonard seems happy for them, but Mrs Maguire can't contain her upset. On his way out of the vicarage the next morning, Sidney spots Mrs Maguire crying, and then encounters Leonard, who is now wondering about his own future, should a less tolerant vicar move in. Sidney feels incredibly guilty but tells Leonard it has to be his decision. In church, Sidney puts on his dog collar and leads a service, thinking his days within the village are now numbered but when a little boy called Jacob is abducted Sidney finds that the community need him more than ever. Meanwhile, Mrs Maguire must prepare for her own future whilst struggling to come to terms with Sidney's imminent departure. Geordie's behaviour grows increasingly erratic as he struggles to cope with the mess he's made of his family life, and as Sidney and Geordie move closer to discovering who has kidnapped Jacob, Sidney must choose to move forward with Amanda in London, or be there for his best friend Geordie in his hour of need.