For more on Mick Herron’s Slough House series go here.

Mick Herron has seemed to enjoy playing in the expanded sandbox of the Slough House universe, writing a novel adjacent to the series, multiple novellas and with The Last Dead Letter, his first short story in the world of the Slow Horses. This story was an exclusive addition to the Waterstones signed copy of Herron’s Joe Country. When I first heard about it, I initially imagined it would be quite short but the story is a rather substantial 30 pages.

The story begins back at old St. Leonard’s, the Spooks’ Chapel, where River Cartwright’s grandfather was laid to rest at the start of Joe Country. Molly Dornan is there waiting to extract her pound of flesh from Jackson Lamb for an earlier favor. In this case, it’s learning the truth to a story Dornan has found in her precious archives. She’s put most of the pieces together but needs Lamb for the last bits of the puzzle. Molly enjoys closing off those unknown loops in her files where ever possible.

The tale she tells is of “Dominic Cross”, an agent runner in Berlin, he’s a little crooked and drinks too much but always looks after his joes. Cross is a veteran of the spy game, but been in Berlin too long. He makes the misjudgment that many spies seem to make – he falls in love. When the Stasi opposition finds a way to turn this against him the question becomes whether he can find a way out of the devil’s choice he’s been given. Does he choose the life of his lover or his joe?

Herron covers a lot of ground for such a short story. He deftly creates the setting of Cold War Berlin, a timeframe he hasn’t written about before, with it’s halved identity. He even manages to sneak in some new terminology – creating something called a mirror-man who is rather like a confessor priest for agents in Berlin, hearing their sins and keeping them on the straight and narrow.

Spoilers ahead –

It wouldn’t be a Herron story without a twist. Herron deftly drops hints along the way that “Cross” is Lamb – Dornan talks at certain points implying that Lamb would know the answer, specific habits that both “Cross” and Lamb have, as well as playing on long time readers eagerness to learn about Lamb’s background and the idea that somewhere deep down in the past there may have been a bit of humanity in him. Of course by the end we find that Lamb wasn’t Cross but instead his mirror-man, otherwise known as The Shit. Herron has stated that we won’t ever see a story with Lamb set in his past, so this short story may be as close as we get.

If you’ve ever wanted to see what Herron would do with a Cold War set story, you owe it to yourself to search out The Last Dead Letter. Like a piece of kids candy, it packs a lot of flavor in a small package starting out with a sweet love story before turning tart at the end.

At the time of posting, editions with the short story are still available on the Waterstones website.