When the dead return to haunt the living, Lockwood & Co. step in. A series of grisly thefts have been taking place across the capital: powerful supernatural artefacts have been stolen, and their warders murdered. In an atmosphere of mounting panic, a mysterious skull in an iron box is unearthed in Kensal Green Cemetery. Witnesses hear it whispering urgently, but the words cannot be understood. Lockwood & Co. will have to use all their ingenuity and skill to uncover the secret of the whispering skull.