Irritating jobsworth Gerry Dawkins from social services calls on elderly eccentrics William and Mary Bingham, but he's sent away rudely by their daughter Selina and her husband Eddie Stanton. Dawkins is also humiliated at the nearby artists' colony run by Maggie Viviani and her partner Adam Grace. He angrily demands a police investigation.


Barnaby's wife Sarah arrives in Midsomer as new head of Causton comprehensive school but deputy Josie Parker seems annoyed at the appointment of an 'outsider'.


The Stantons run a stud farm with Maggie's son Ben - who is in love with Eddie's daughter Verity. Next door, the Binghams live as recluses in upper class squalor, surrounded by towering piles of newspapers and empty pizza boxes. They only communicate through solicitor Laurence Fletcher.


Dawkins phones Jones, claiming he has urgent information but Jones fobs him off. Then his body is found in the river near his canoe. A guilty Jones learns Dawkins was planning to meet Maggie and Adam. He'd also printed off a map of the moon.


Maggie - who has a gift with horses - visits the stud farm to soothe a nervous stallion, while Selina forces a protesting Ben to take her to bed. Later, Verity announces she and Ben are getting married. Selina is shocked and slashes Maggie's paintings with a knife.


After Barnaby eventually meets the Binghams, he learns they were once happy 60s kids who never recovered from losing their elder daughter and son in a drowning accident. Their children crashed their speeding car into a river following a family row.


Eddie has been spotted 'visiting' Josie Parker, but it turns out that she's not his mistress but his bookkeeper and Eddie's been fiddling his accounts.


Mary invites Barnaby to tea as he discovers that Jennifer's body was never found. But before he can get to Bingham House, Mary is crushed by a tower of newspapers. Could a mysterious reference to a moon crater called Bingham hold a clue? Meanwhile, the Bingham's old family doctor confirms that Jennifer was thrown out of the family home because she was pregnant. But the old man dies before he can say more.


With everyone summoned to the stud farm, Barnaby reveals that Maggie is really Jennifer - she chose the name Viviani after another moon crater. But there's more shocking news - Ben's father was her brother Robin. Selina is thrilled to be reunited with her sister, but who killed Dawkins to keep the truth hidden?


Just then, Jones discovers William Bingham sitting atop a pile of newspapers - holding a detonator to a bomb up in the rafters...