"A terrible crime forces Lockwood to turn to Lucy for help, setting them on the trail of dark secrets at the heart of London society. Both professionally and personally, their investigation stirs up forces they may not be able to control. . . "--

When Will Burrows and his friend Chester embark on a quest to find Will's archaeologist father, who has inexplicably disappeared, they are led to a labyrinthine world underneath London, full of sinister inhabitants with evil intentions toward "Topsoilers" like Will and his father.

"Lockwood & Co. are hired to investigate Edmund Bickerstaff, a Victorian doctor who reportedly tried to communicate with the dead, while Lucy is distracted by urgent whispers coming from the skull in a ghost jar"--

In the beautiful Cartier makeup compact she bought at a flea market, Phoebe finds a letter written during World War II in London, from one sister to another, which contains a "spell" for bringing people closer together, a kind of treasure hunt around London--and Phoebe could really use such a spell, because her older sister, Alice, will be leaving for university soon, and just now she seems to be cutting Phoebe out of her life.

"With the help of some unexpected, and rather ghostly, allies, Lockwood & Co. must battle their greatest enemy yet, as they move ever closer to the moment when the earth-shattering secret of 'the problem' will finally be revealed"--