From million-copy bestselling author David Walliams comes his first ever murder mystery – with thrills, spills and laughs galore. A Waterstones Best Children's Book of the Year Dilly loves a good murder. Not a REAL murder. A made-up murder. One you would find in a murder-mystery novel. Sherlock Holmes is her favourite detective. She even named her dog Watson after his faithful companion, and trained him to sniff out clues and follow trails. So far, Dilly and Watson haven't cracked many cases – beyond lost cats, or missing biscuits that turned out to have been eaten all along. But now the detective duo find themselves on a luxury ocean liner bound for London. A thousand passengers. A thousand miles of ocean around them. It's the perfect place for a murder... Or two. Or three. Or four. Or MORE!