Roald Dahl started with a good black-comedy idea: wife kills husband with a frozen leg of lamb, then cooks the lamb to dispose of the murder weapon. The story was written in the 1950s when Americans were buying big freezers and filling them with meat, thinking they could save money by buying in quantity at wholesale prices. The fad did not last. Electricity rates went up, there were power blackouts causing spoilage, and the frozen meat probably didn’t taste as good as fresh.

It was a stroke of genius to make Patrick Maloney a cop. This strengthened Mary’s alibi enormously because cops make many dangerous enemies. The investigators naturally supposed that Patrick had been the victim of some felon, or a friend, relative, or hit man hired by that felon. The Maloney house was full of cops because they were giving special attention to a murder of “one of their own.” They spent many hours searching for the murder weapon, giving Mary plenty of time to cook the lamb thoroughly.

The story might not have worked as well if Patrick had not been a cop. In inside domestic murders suspicion usually falls on the spouse. Dahl portrays Mary as being an exceptionally docile, devoted wife, so it would be hard to imagine her killing anyone with a heavy blunt instrument. But it would also be much harder to imagine some killer entering the home during the short time she was at the grocer’s if Patrick had not been a cop.

One wonders what a really good detective, like Columbo as played by Peter Falk on television, would do. The Columbo stories usually involved someone who planned the perfect crime, only to be trapped by a tell-tale clue. Columbo would have inspected the freezer. He would have taken out all the frozen meat looking for the murder weapon, and he would have noticed that the meat itself was rock-solid. This could have led him to suspect that the leg of lamb he smelled cooking could have made a perfect weapon in its frozen state. A leg of lamb is different from other roasts because the bone provides an ideal handle.

A good detective (which the investigating officers were not) might have found out that Patrick Maloney had some reason for wanting a divorce--although Dahl is careful to portray him as a strong, silent type.

She loved the intent, far look in his eyes …  and especially the way he remained silent about his tiredness, sitting still with himself until the whisky had taken some of it away.

There are several details apparently intended to suggest that he spends his evenings at home, so that he probably isn’t having an affair.

When the clock said ten minutes to five, she began to listen, and a few moments later, punctually as always, she heard the tires on the gravel outside…

Other details suggest that he keeps his thoughts to himself, so perhaps he hasn’t discussed his domestic relationship with anybody else.

“So there it is,” he added. “And I know it’s kind of a bad time to be telling you, but there simply wasn’t any other way. Of course I’ll give you money and see you’re looked after. But there needn’t really be any fuss. I hope not anyway. It wouldn’t be very good for my job.”

Mary is able to bring off a perfect crime because she is a devoted wife, her husband has no known reason for wanting a divorce, nobody knows he has asked for a divorce, the investigating cops are not super-sleuths, Mary knows how cops think because she is a cop’s wife, and she gets them to eat the murder weapon.