Two couples disappear from the tiny village of Monks Barton, leaving their half-eaten breakfasts on the table. Barton Woods is said to be haunted and Peter, son of one of the couples Molly and Colin Thomas, died after getting lost there.


Pompous cleric Rev Wallace Stone tells Barnaby that the monastery was destroyed in the 16th century. According to legend, the cries of the slaughtered monks can still be heard.


The other couple, Stanley and Nesta Goodfellow, are caretakers of The Priory, owned by Lynton Pargeter. At the imposing house, Barnaby inadvertently traps Jones in an iron maiden - a medieval instrument of torture. Later, psychic Cyrus LeVanu conducts spiritual healing in the woods. To his horror, he unearths a man's body.


Postman Sam Nelms is having an affair with Sarah Stone, wife of the clergyman. He's also taken a Japanese miniature destined for one of the cottages instead of posting it. Barnaby suspects it was originally stolen from The Priory.


Cyrus is burning ceremonial fires in the woods as Pargeter finds Molly Thomas in her cottage, lying in a pool of blood. She was shot in the back. Jones and Barnaby try to follow a car through the trees. Instead they find a deranged man wailing in a shack - it's Stanley Goodfellow. Doctors say he has experienced something so terrifying that his mind has closed down.


The mystery victim was a member of a London gang involved in antique theft. Was he connected to Pargeter? Meanwhile Rev Stone goes to exorcise the woods and finds Colin Thomas's head sticking out of the ground.


Jones discovers Nesta was planning to leave Stanley as LeVanu goes into a psychic trance, claiming the missing woman is in a dark place. Pargeter is seen loading furniture from The Priory into a car.


Barnaby discovers the source of the eerie cries and blames LeVanu while Jones finds that Pargeter was fencing stolen antiques. Then Stanley disappears again. Believing Pargeter is involved, they rush to The Priory where they find him dead, impaled inside the iron maiden. Can the detectives make the link between the missing couples and the stolen antiques and find Nesta before it's too late?