SPUD – the Super Perceptive Undercover Detectives – have another mystery to solve! When there's a treasure heist on a school trip to the Tower of London, it's up to Callie, Grace and Bo to crack the case! Having magical hearing aids and a Spy in the Sky might just come in handy... Karen Owen has been partially deaf since childhood, and wrote the character Callie in Major and Mynah to reflect who she wanted to be when she was younger – funny, clever and with a special gift to hear something that other people could not. She was brought up in Kent and currently lives in London.