After her previous solo escapades around Europe, Lettice Breech?s father is nervous to go away for business without her. Safe in their home city, and in the care of an enthusiastic young guardian named Hera Goodchild, Letty is happy to stay behind. With their trusty butler Fortnum to look out for her and cook Nell to make delicious food, surely the time without Pa would simply fly by? But despite her very best intentions not to stir up any trouble, Letty soon finds herself embroiled in a thrilling new mystery. There are secret notes in newspapers exchanged with an enigmatic frenemy, puzzling clues in dictionaries that lead Letty on a whirlwind treasure trail around 18th century London, and - nearly - a murder . . . In her continued search for truth, can Letty use her deductive skills to unravel the mystery of the word thieves?