Anthony, George, and Lucy investigate new hauntings, track down assassins, and a new assistant joins Lockwood & Co.

Follows three young operatives of a Psychic Detection Agency as they battle an epidemic of ghosts in London.

Investigating a string of disappearances amid supernatural occurrences in London, Alex and Ren discover the workings of a powerful Death Walker intent on destroying the city.

Having upset the balance between the warring statues of London, twelve-year-old George is confronted with new challenges as he tries to free his captured friends Edie and The Gunner from the formidable Walker and deal with the three strange veins of marble, bronze, and stone that have begun to grow out of his hand.

Fifteen-year-old Miss Penelope Lumley, a governess trained at the Swanburne Academy for Poor Bright Females, takes the three Incorrigible Children of Ashton Place to London, England, and learns they are under a curse.

As Will Burrows continues to search for his lost archaeologist father in the strange underground world he has discovered, he stumbles across a sinister plot with terrible implications for the world above.

When thirteen-year-old Gerald finds himself the heir to twenty billion pounds from an aunt he never met, he inherits with it a mystery surrounding his aunt's death and various artifacts in the British Museum.

Miss Penelope Lumley assuages the disappointments of her sixteenth birthday by accepting an invitation to speak at her former school, the Swanburne Academy for Poor Bright Females, which will be closed if she cannot prove the academic progress of her incorrigible charges.

Spurred on by his youngest sister, Rose, twelve-year-old Indigo sticks up for himself and an American boy who has replaced him as the primary target of the school bullies.

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.-- Provided by publisher.