As the story opens, the Austin family has settled in a New York City apartment after the events of "The Moon by Night", and made some friends; blind young pianist Emily Gregory and Josiah "Dave" Davidson, who helps Emily get around. Emily is studying under the tutelage of the passionate, leonine Emmanuel Theotocopulous, better known as Mr. Theo. Canon Tallis, newly arrived at the Cathedral of Saint John the Divine after the events of "The Arm of the Starfish", meets the Austin children and their friends just as they encounter an anachronistic Genie in a junk shop. Tallis advises and helps to protect the children as they are drawn into a mystery involving the Genie, a street gang called the Alphabats, and the local bishop's strange behavior.