?Clever, inventive and a cracking read' - Eoin Colfer, author of Artemis Fowl, on THE CLOCKWORK CONSPIRACY

Isaac and Hattie have been invited to a high-profile event at the French National Archives in Paris to celebrate their achievement in saving time. But as Isaac prepares to make his speech, the lights go out and a single shot is fired.

The police think it was an assassination attempt on the infamous businessman Balthazar Blaise, but Isaac and Hattie realise that something very different is going on when they discover a boy taking something from the archives before vanishing without a trace.

As they investigate, Isaac and Hattie are pulled into an underground world, searching secret and forgotten places for a stolen letter, a missing sister and a map that will unearth a long buried secret ...

Sam Sedgman is a bestselling author, confirmed nerd and enthusiastic ferroequinologist.

Before writing stories for children, Sam worked as a digital producer at the National Theatre, which meant nosing around backstage with a camera and a microphone, cajoling theatre makers into explaining how stories get made. Forever interested in piecing things together, Sam is a lifelong fan of puzzles, games and detective fiction, and once founded a company making murder mystery treasure hunts for adventurous Londoners. His books have been translated into more than 20 languages.

When he isn't writing, Sam can usually be found admiring a handsome timepiece, watching Alfred Hitchcock movies, or explaining some weird fact to you. He lives in London, on top of a railway station.