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'One of the finest mysteries I have ever read.'
Rob Rinder, Sunday Times bestselling author of The Trial

'A tantalising mystery for word sleuths and crime fans alike.'
Janice Hallett, Sunday Times bestselling author of The Appeal

A coded letter. A missing woman. A truth waiting to be found.

When an anonymous letter is delivered to the Clarendon English Dictionary office, it becomes rapidly clear that this is not the usual word-related enquiry. Instead, the letter hints at sinister events linked to a particular year.

For editor Martha Thornhill, the date can mean only one thing: the summer her brilliant older sister Charlie went missing. Ten years on, Martha and her family are no closer to unravelling the mystery of Charlie's disappearance - until now.

As more letters arrive, Martha and her team follow the linguistic clues to a troubling truth. It seems Charlie was keeping a powerful secret, and that someone is desperate to keep it well and truly buried.

Guilty by Definition is a love letter not only to language but to the city of Oxford, wrapped within an intriguing mystery of a missing woman and considering the emotional aftershocks of her disappearance on those left behind.

SHORTLISTED FOR THE BRITISH BOOK AWARD 2025: BOOK OF THE YEAR - CRIME & THRILLER

[Guilty by Definition was a Sunday Times bestseller in August 2024]