The Talent Thief by Alex Williams

Wealthy orphans Adam and Cressida Bloom couldn't be less alike. Adam can't seem to help being exceedingly ordinary whereas Cressida, his glamorous sister, has a magnificent talent - when she sings, even the birds stop to listen. Then Cressida is invited to perform at Fortescue's festival of young talents and Adam tags along.

But once the children arrive at the festival, in a mountain-top hotel, their terrific talents begin mysteriously to disappear. A piano virtuoso suddenly forgets how to play, a maths genius finds she can no longer multiply. There's a sinister shadow that only Adam ever sees, a strange glow emanating from behind closed doors...With the help of an erratic ex-racing driver, dashing Amy Swift, Adam and Cressida rip-roar off through the mountains in Amy's shiny racing car, the Silver Swift.

They are in perilous pursuit of the dastardly talent thief! But from a hair-raisingly close shave with an avalanche to crash-landing a plane on a runway the size of a table, Adam never gives up. Perhaps he isn't as ordinary as he first thought!