Cecily Sawyer has spent the evening in the attic, training her pet mouse, Mrs Maple Syrup – an unusually intelligent mouse, in Cecily’s opinion – when her parents disappear. Luckily, Cecily is more than ready to investigate such a thing.

She has wanted to be a spy her whole life, and has all the spy handbooks, manuals and code-cracking kits a girl could need. But soon, Cecily discovers several very strange things in her city. She’s not the only spy out there – far from it, in fact.

And Mrs Maple Syrup is not the only unusually intelligent mouse…