The Demons of Constantinople

In the year 1372, the space-time continuum has been breached and demons of all kind, evil and benign, spill from the netherworld into the human one. Pucorl, one of the demons who comes across the rift, accidentally brings with him a van from the Paris of the twenty-first century. The van is filled with a drama teacher, her son, and eight high school students-along with all of their electronic devices.
Soon, more demons arrive, many of whom are entranced by the electronics of a future world. Laptops, tablets and cell-phones-not to mention the van's equipment-become possessed by imps and spirits of the netherworld.
After defeating the demon lord Beslizoswian and the French prince he had seduced to evil, Pucorl and his teenage allies from the future go to Constantinople. Perhaps in that great city full of scholars they can find the means to close the rift between the universes.
But when they arrive, they find that Constantinople is a nightmare of its own. Imperial intrigues abound, as do those of the Church's patriarchy. Still worse, the city is plagued by demons and sorcerers of all kinds. And to cap it all, the sultan of the Ottoman Empire has enslaved an afreet and plans to use the great ancient monster to conquer the Byzantine Empire-starting with Constantinople itself.