Season 09 Episode 06

Marcus Blakely takes Geordie and Larry to a bone he has turned up on his land. Larry suggests it might belong to a girl who went missing after going to the pictures, and Geordie points out she would not have been carrying a sword. The skeleton is a Roman soldier, and the Romans were at Cambridge in about 70 AD, which Jack Chapman knows because he worked on archaeological digs when he was younger. Jack becomes the village's authority on the find and is delighted about it.

Three archaeologists come from Oxford to excavate the skeleton and search the surrounding field: Professor Henry Waddingham, Kate Earnshaw and a young man called Billy Randall. There is a relic to show off at once, a cross found in the soldier's hand. At a talk at the village hall Billy says the cross is Byzantine, and Jack objects that a Byzantine cross cannot belong to a Roman soldier because the dates do not fit. Waddingham corrects Billy and says the cross is Flavian, and then asks the assembled villagers for donations to fund further digging. Alphy attends, because Kate has taken an interest in him, and so does David Lane, the vicar of Newnham, who has come to meet the congregation he will inherit when the parishes merge. Mrs Chapman is furious about him. Alphy has become resigned to his own removal and says he is waiting for a sign that it is God's will, which Geordie finds infuriating.

Geordie has the same problem at home, from the other direction. Cathy is calm and he finds it unnerving. She has not told him that she is taking the mood stabilisers Dr Bennett prescribed, and when their daughter Dora breaks one of Cathy's vases she barely reacts. Geordie buys her a dress and proposes a dinner out, she says she is too tired, he asks what is wrong with her, and she answers that she thought this was what he wanted.

The next morning there is a second body next to the skeleton. It is Waddingham. Billy, who was his pupil at Oxford and treated him as a father, is devastated. Kate is less affected until she finds that the cross has gone and accuses Billy of having left it out to be stolen, and Billy then finds that his rock hammer has gone from his tent. Alphy had seen Waddingham arguing the night before with Della Blakely, who owns the farm with her husband Marcus. Della is sceptical of the whole enterprise and believes the archaeologists are profiting from her land, saying the Blakelys were promised a share of the donations and will never see it. She took the cross. She and the two archaeologists argue over who owns it, and Alphy takes it and says he will keep it until ownership is settled.

A notebook in Waddingham's effects carries an appointment with an antiquities dealer marked NQA, and Jack explains the letters: no questions asked. Waddingham was selling finds on the black market, and Jack's view is that the distance between an archaeologist and a thief is short. Kate's credentials do not survive contact either: she claims to be a curator at an Oxford museum and the museum says she was dismissed for stealing from its collection. The museum director adds that Waddingham was a grave robber. Waddingham had a substantial balance in his account and a buyer already lined up for the cross, which means he intended to sell it without telling his colleagues. Geordie and Alphy search Kate's bag in front of both archaeologists and find Billy's rock hammer, bloodstained. Questioned at the station, Kate is defiant and treats the interview as an opportunity to interrogate Alphy, telling him he looks lost and asking what happened in his past.

Alphy's week gets worse. He goes gambling in a seedy bar and is approached by a young woman who introduces herself as Petra, a student, who takes him back to her room at her college for the night. Returning to the vicarage in the morning he finds the door open and his study ransacked. The cross is still there. He takes the break-in as the sign he asked for and concludes that he should accept the decision to remove him from Grantchester. Geordie sees Billy meet Marcus Blakely in the pub and hand over an envelope, and then takes Billy's remark about the cross being Byzantine to Jack, who confirms it: the relic is Byzantine and therefore centuries too late to have been held by a soldier of that skeleton's date. The consequence is the one the case turns on, since when Waddingham overruled Billy in front of Jack at the talk, Billy understood that his teacher was lying. Asked about the envelope, Marcus says it was money and Billy says it was what Waddingham owed the Blakelys for the use of their land, and Billy and Kate begin packing to leave.

Kate Earnshaw stole the cross from the museum that dismissed her and gave it to Waddingham, who planted it with the skeleton so that the village would believe there was more to find in the Blakelys' field and would fund further digging, and Waddingham then intended to sell the cross himself, behind her back. Billy worked it out when Waddingham contradicted what he knew to be true about the cross, and confronted him. Billy killed him with the rock hammer and put the hammer in Kate's bag to shift the blame. The episode ends with Marcus still digging his field in hope, against Della's wishes.

The household threads move on. Geordie glues Cathy's broken vase back together and gets very little response. Mrs Chapman, who has understood what is actually happening to Cathy, tells her that she is not in decline, that she is going through the menopause and does not need pills, and Cathy decides to stop taking them. At the vicarage Mrs Chapman writes letters on Alphy's behalf in an attempt to keep him in Grantchester, and she, Leonard and Jack form themselves into a committee for the same purpose. Daniel, meanwhile, has been asking Jack for money to support Sam White's work and is now putting his own money and his own time into it, which Leonard discovers only when Jack tries to apologise to him about Daniel. Leonard confronts Daniel, who accuses him of always walking away and says that Sam predicted it.

The episode's clue is a date, since a Byzantine cross is several centuries too new to have been held by a skeleton of its period, and the only person who could be certain of that is the pupil who was corrected in public. The planted relic is a fraud designed to raise money from a village that has just been told to fund the dig, which makes the motive for the murder the exposure of the con rather than the con itself. Cathy's vase is the quiet counterweight to all of it, since the husband gluing it back together is doing the thing the archaeologists were pretending to do.