There are only two main characters in "Lamb to the Slaughter." They are Mary Maloney and her husband Patrick Maloney. Patrick is a policeman and has been on the force for many years. Mary is a housewife. She is six months pregnant. After she kills her husband with a frozen leg of lamb she is the only main character. She is the viewpoint character from beginning to end.
There are a number of policemen investigating the murder, but none of them stands out as an important character. This is interesting. It shows Roald Dahl's thinking. He doesn't want to create a smart detective like Columbo played by Peter Falk on television. Such a detective might see differently, think differently, and ask different questions. Dahl didn't want to have a story which featured a battle of wits between the killer and the cop. The detectives who come to investigate the crime are all of a kind--not very intelligent or imaginative.
Patrick is obvioiusly the strong, silent type. Dahl does not explain why he wants a divorce, but it seems obvious that Mary is driving him nuts with all her attention. These are some of the things she says to him in just a few minutes after he arrives home:
"I'll get it!" she cried.
"Darling, shall I get your slippers?"
"Darling," she said. "Would you like me to get you some cheese?"
Finally, after having two very strong whiskey highballs, Patrick says:
"Listen, I've got something to tell you."
Dahl is a good writer. He knows it is unnecessary to quote what Patrick tells his wife. It is obvious from his drinking and his body language, as well as from her suffocating attentiveness, that he tells her he wants a divorce and also that he feels especially guilty about announcing it now that she is six months pregnant.
It didn't take long, four or five minutes at most, and she sat very still through it all, watching him with a kind of dazed horror as he went further and further away from her with each word.
The fact that Patrick is a cop and Mary a cop's wife is important. His murder brings an exceptional number of men to investigate, while, as a cop's wife, Mary knows a lot about establishing an alibi and bringing off a perfect crime. The other cops spend a long time looking for the murder weapon. This makes them tired and hungry, and it gives Mary enough time to turn the frozen leg of lamb into a delicious roast. The other cops would not normally accept a dinner invitation from the wife of a murder victim. It would be strictly against the rules. But since they regard Patrick as "one of us," they also regard Mary as "one of us." So they break the rules and eat the entire leg of lamb.
The most striking feature of "Lamb to the Slaughter" is Mary's abrupt change from a loving, devoted, submissive, attentive wife, not only into a murderess, but into a perpetrator who is clever enough to fool a whole house full of policemen by establishing an alibi, cooking the murder weapon, and feeding it to the very men who are searching for it. It would seem that just as Patrick was building up a loathing for his clinging wife, she was building up a strong unconscious resentment of a man who did not appreciate her love and devotion. Something very similar happens in Dahl's story "The Way Up to Heaven."