Deaths on the River.
"The evidence, Sir:
"The Wallaces' marriage is in difficulties. At six o'clock, Mr Wallace tells his wife he's going home but actually goes drinking in The Granta. His behaviour is worrying and he is thrown out about eight.
"Meanwhile, Mrs Wallace and Mr Sammy are seen holding hands at a restaurant. Shortly before eight, Mrs Wallace and a man hire a punt and head towards Grantchester, returning within the hour. The boatman sees them kissing passionately before parting.
"At dusk, eight-thirty, a dog walker hears raised voices on the river bank.
"The bodies of Mr Sammy and Mr Wallace are found a mile from Cambridge opposite each other on different sides of the Cam. There are no bridges nearby and both bodies are dry. Both died from an overdose and had high blood alcohol. A pill box beside Mr Sammy has both men's fingerprints. Neither leaves a note."
"So, Sergeant, the men shout at each other across the river, Mr Wallace takes an overdose and throws the pills to Mr Sammy who does likewise. They're drunk and acting on impulse, so no suicide notes. But why would both kill themselves?"
"The man in the punt wasn't Mr Sammy, Sir."