This 1973 title was the 74th and final novel that author Agatha Christie ever wrote, in addition to the last in her sequence of Tommy and Tuppence adventure stories. (Unlike for her better-known detective series, she did not set aside any additional installments for posthumous publication.) I won't speculate about the writer's declining mental faculties at this stage of her life as I've seen other reviewers do, but I will say that this book is easily the worst of its lot and a bit of a sour note to end on.

Among its stronger qualities: our married protagonists have continued to age, and are now moving into a new home in their 70s. Their banter back and forth is as affectionate as ever, and their instincts as retired spies / investigators remain relatively sharp. I also love their dog, whose perspective in a few key scenes is a fun change of pace for the narrative.

The premise is both absurd and poorly developed, however. In examining the books that the previous owners have left behind in the library, Tuppence discovers a secret message in one of them: underlined letters that spell out, "Mary Jordan did not die naturally. It was one of us. I think I know which one." She eventually learns that the woman in question was a spy during World War I, and that the boy who owned the book perished soon afterwards himself.

Two former intelligence agents happening to uncover a relevant plot at their doorstep is as silly as those times when Poirot or Marple stumbles across a fresh murder whilst on holiday, and the actual investigation here mostly consists of asking older folks in the community what they remember from long ago (and receiving contradictory information in reply). The couple's own contacts in the business, meanwhile, are justifiably convinced that the Beresfords know more than they're letting on about the affair and have moved into this particular address specifically to pursue the case further.

Yet it's not entirely clear what that pursuit entails. They're not seeking to identify the killer -- nor do they, in the end -- and the clues that they find are largely other things that have been left sitting in the house for decades, suggesting that no one cares any longer or has ever bothered to cover their tracks. Nevertheless, someone in the present day is apparently trying to stop or even kill the heroes for looking into the matter, though their motivation isn't explained and their traps are so ineffective it's a wonder that they're noticed at all.

Anyway. Nice to check in on Tommy and his missus one last time, but their best days are firmly behind them at this point.

This volume: ★★☆☆☆

Overall series: ★★★☆☆

Volumes ranked: 1 > 3 > 4 > 2 > 5

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I regret reading this book. It was long and boring with quite a lot of repetitions.

Not Dame Agatha's finest hour - Tommy and Tuppence never appealed to me much and this is very dull indeed. Two stars for Hannibal the dog, though...

I really liked this one, which is surprising because generally when I read Agatha Christie novels I wind up thinking 'meh' whenever someone recommends one to me. I'll have to look for more in this series!