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.