Dark things are massing from the remotest corners of the Immaterum, where the realm fractures and merges with other inhospitable regions. These are the lost and insane; demons, spirits and ancient gods without names or worshippers. Something is calling and uniting them with deadly purpose.

Because of his close affinity with the Immaterium Professor Abbacus can hear the monsters coming. He has fought them before, back in 1895 when they were united by the Martians. But he can't understand them or determine their new mission. At his wits' end he is finally forced to seek help from an old enemy.

Meanwhile another blast from his past finally reaches the Nocturnal Academy. This person has been hunting him for decades, following minute clues across the country, but for what purpose? To rekindle an old friendship? Or to kill him for leaving them behind?

To fight the approaching evil everyone at the Nocturnal Academy must be on high alert for anything even slightly out of the ordinary. Because even the sweet old folks of the Appleton Seniors Meditation and Tai Chi Group might not be exactly who they appear.