The Falcon's Malteser — Anthony Horowitz

From the # 1 New York Times bestselling author of the Alex Rider series. 

When the vertically-challenged Johnny Naples entrusts Tim Diamond with a package worth over three million pounds, he's making a big mistake. Tim Diamond is the worst detective in the world. Next day, Johnny's dead, Tim feels the heat, and his smart younger brother, Nick, gets the package -- and every crook in town on his back!