N or M? by Agatha Christie

"But I suppose even you couldn't persuade your wife to keep out of danger."
Tommy said slowly:
"I don't know that I really would want to do that... Tuppence and I, you see, aren't on those terms. We go into things - together!"
In his mind was that phrase, uttered years ago, at the close of an earlier war. A joint venture...
That was what his life with Tuppence had been and would always be - a Joint Venture...

Agatha Christie's second detective novel, The Secret Adversary, featured two young adventurers in 1919 named Thomas Beresford and Prudence (nicknamed Tuppence by her family) Cowley who stumble on a mystery and fall in love. Christie would go on to write 3 more novels and a book of short stories about Tommy and Tuppence over the course of her career, and in each book the couple were shown to have aged and moved into different stages of their married lives together as time passed in Christie's real world.

In the second book, Partners in Crime, the book of short stories set in the 1920's, Tommy and Tuppence are married and open a detective agency. Each story is a case they undertake and each case is written to reflect the style of other famous fictional detectives, including Christie's own Hercule Poirot. At the end of the book Tuppence announces her pregnancy.

N or M? finds the Beresfords middle aged and eager to find exciting work at the outbreak of WWII now that their twins Derek and Deborah are grown and off having adventures of their own as part of the war effort. Despite the fact that public opinion states that gray hairs like Tommy and Tuppence ought to be sitting at home knitting or typing for England, they are determined to throw themselves headlong into danger and thrills and end up, of course, embroiled in an espionage thriller involving Nazi operatives and fake identities and invisible ink and secret messages.

The Beresfords are lovable pair of, essentially British, characters. Tommy seems to be the most boring, safe, unassuming guy on the planet, but deep down he longs for excitement and never holds Tuppence back. Tuppence, on the other hand, is feisty and daring and smart, and she chafes against the expectations society holds for her as a woman and a mother. They are tender and hilarious together, and completely believable as a couple in unbelievable circumstances.

"I have often noticed that being a devoted wife saps the intellect," murmured Tommy.
"And where have you noticed that?" demanded Tuppence.
"Not from you, Tuppence. Your devotion has never reached those lengths."
"For a man," said Tuppence kindly, "you don't really make an undue fuss when you are ill."

The last two novels are By the Pricking of My Thumbs, published in 1968, and Postern of Fate, published in 1973. In the former, Tommy and Tuppence are grandparents in their 60's, and in the latter they are "retired" and in their 70's. Postern of Fate was the very last novel Agatha Christie ever wrote.

Most of the time Christie fans debate whether Poirot or Marple is the better of her detective characters, but I love the Tommy and Tuppence books best. I wonder as well if Agatha herself didn't love them more since she returned to them repeatedly, although not often, as the decades rolled by, checking in on their progress as though they were old friends. Perhaps Tuppence even resembles the real Agatha or else the person Agatha wished to be. They were the same age always, so I wouldn't be surprised. At any rate, the books are a lot of fun and a nice little window on history.