Michael Broad 
Ghost Diamond! 

Secret agent Amelia Kidd has saved the world loads of times from evil geniuses and criminal masterminds-thanks to her great disguises, gadgets (which sometimes work), and her brilliance at improvising in sticky situations. The three secret agent case files in this book are:The Case of the Ghost Diamond, in which Amelia foils a daring jewel theft during a class trip to the museum, thanks to her convincing granny disguise and her mirror-on-a-stick gadget.The Case of the Cat Nappers, in which Amelia discovers the reason for all the disappearing cats in her area-they have all been trained to become burglars! Cat burglars! Luckily Amelia’s quick thinking foils the robbery and catches the thieves!The Case of the Whispering Weeds, in which an innocent trip to the garden center results in Amelia meeting an evil genius who has cultivated a weed army to control every crop on the planet. Weed killer-and Agent Amelia smarts-to the rescue!