Lucy, a girl with psychic abilities, joins two boys, Anthony and George, at the ghost-hunting agency Lockwood and Co. to fight the deadly spirits plaguing London, doing their best to save the day without any adult supervision.

In London, where the most gifted teenage ghost-hunters venture nightly into perilous combat with deadly spirits, amidst the many corporate, adult-run agencies, one stands alone: independent of any commercial imperative or adult supervision a tiny startup, run by two teenage boys and a newly arrived, supremely psychically gifted girl, a renegade trio destined to unravel a mystery that will change the course of history.