Family life is far from normal at the home of Eileen Fountain, the steward at prestigious Whiteoaks Golf Club. Eileen has thousands of pounds in bank notes and treats her younger son Darren, a wannabe golf pro, like landed gentry. Her other son Colin, a greensman, is relegated to manual tasks and beans on toast.


At nearby Pellings, a rambling manor house, club captain Martin Crisp is trying to buy back the home once owned by his family from golfing president Will Tunstall.


Snooty members of the club, including the self-styled Silver Foxes Alistair Kingslake, Jerry Drinkwater, Ed Monkberry and Miles Tully, are dismissive of the village members, who are allowed on the course for a few hours a week. When Kingslake bets Drinkwater £1000 at the 13th hole, disaster strikes. Kingslake is struck on the head by a golf ball and angrily strides into the rough to find the culprit - only to be bludgeoned to death.


As Barnaby and Jones investigate, Bullard reveals that the notorious 13th hole is known as Crisp's Folly - a vicious dogleg and the place where Martin Crisp's grandfather gambled away his home.


Miles Tully suggests Kingslake may have cheated at golf before he was killed, while Jones goes to take a statement from Ed Monkberry. But instead he finds him in the woods, dead from multiple stab wounds.


Bullard reveals that Kingslake was killed by two different golf clubs as Jones learns of an earlier assault at Crisp's Folly - on Derek Painter, a friend of the Barnabys. Harry Claypole, a village member, reluctantly admits there were other attacks not reported to the police. He's hoping to be elected as a full member of the club, as is Darren.


Barnaby discovers Eileen is running a lucrative money-lending operation to members who can't pay their gambling debts, including Drinkwater and Derek Painter. Colin uses force when the payments fall behind. But is there any connection to the murders?


As the killer is revealed as a left-hander, Barnaby realises the deaths could be linked to the imminent meeting of Whiteoaks' membership committee. But who has the most to lose if the club blackballs Darren or Claypole?