Teodora has always longed to visit Venice, and at last she has her chance. But strange and sinister things are afoot in the beautiful floating city. Teo is quickly subsumed into a secret world in which salty-tongued mermaids run subversive printing presses, ghosts good and bad patrol the streets, statues speak, rats read, and librarians fluidly turn into cats. And where a book, The Key to the Secret City, leads Teo straight into the heart of the danger that threatens to destroy the city to which she feels she belongs. An ancient proverb seems to unite Teo with a Venetian boy, Renzo, and with the Traitor who has returned from the dark past to wreak revenge. . . . But who is the Undrowned Child destined to save Venice?