Maths-whizz Alice has already solved a mystery or two. Persuaded by wannabe sidekick Sammy to investigate a scientist's disappearance, she's soon entangled in her trickiest case yet.

Dr Learner is reputed to have invented an invisibility suit, but is whacky science really to blame for his vanishing? With the unlikely help of erstwhile nemesis Kevin, Alice solves the puzzle - only to face another.

Should she reveal the truth, or protect her most devoted friend?