The Vanity Case by Niall Teasdale

In 1962, the Collapse happened and the world changed. Officer Sondra Blake of the NYPD went insane overnight and spent the next decade in a mental institution hastily set up to handle people like her, people afflicted by the magic which had suddenly appeared on Earth.

In 2018, Sondra is the most senior detective in the NYPD’s Arcane Crimes Unit. Presented with a new partner, Sondra gets no time to train him as they are thrust into a new murder case with some worrying overtones. A young woman has aged to death in a few minutes while apparently collecting a barrage of disease symptoms she could not possibly have. Someone has used demonic magic to kill her, and the only suspect is the suave, handsome leading actor of an action movie being shot in New York, Dillan Archer.

With tension rising toward riots in Orctown, Sondra and her partner, Clarke, must track down a serial killer who has remained undetected for decades before the current run of victims ends and the killer vanishes again for another seven years.