Mary Mulligan is in quite the pickle.

Not only has she flogged the same small boat to seventeen separate customers (a personal best), but she's only just discovered it belongs to Uego Paramour-local crime queenpin, cultural menace, and woman not best pleased when people sell her belongings out from under her nose. Now Mary's on the run through the winding alleys of The Rook, with Paramour's top assassin, Charlie "Braces"-a man with too many crossbows and not enough chill-hot on her trail. Worse, Mary also happens to be the sole witness to the sudden and rather dramatic demise of a woman who appeared to be minding her own business... while floating past on a magical umbrella. As hiding places go, Mary's current situation is both unexpected and deeply inconvenient: She appears to have accidentally become a nanny. She's not quite sure how, but the pay is decent, and the disguise has held - so far. Unfortunately, the children are hideous. A peculiar man named Albert with a questionable accent has started following her about. The umbrella is once again stolen. And there is, for reasons best not examined too closely, a penguin named Fishy Dave living in the nursery. The fact that it sounds just like a donkey is neither here nor there. And if all that wasn't bad enough, she keeps bursting into song. Against her will. It's a chase! It's a heist! It's a nanny-led crime spree with jazz hands! Hold on to your parasols, it's... Superfloppylazywhineybratalocodocious!