Maisie is intrigued by a new lodger, Mr Fred Grange, who isn't quite what he seems...Mr Grange claims to work as a clerk for a biscuit company, but he's out and about on the London streets at odd hours, and Maisie soon discovers something very precious hidden in his rooms. Determined to unmask him as a thief, she soon discovers that the truth is far more complicated - and dangerous. Before long, Maisie and her friends are led into a web of mystery lurking underground.
