Doctor Who fan fiction.
With the epigraph 'A story which never happened', 'Jenny' takes an alternative approach to the 1989 Doctor Who serial 'The Curse of Fenric', in which an army base in Northumbria was over-run by Haemovores (vampiric creatures that feed on blood, who are one possible end result of humankind's future evolution), under the control of the Ancient One, the most powerful of the Haemovores, and Fenris, an evil from the dawn of time (who bears some similarity to Fenrir, the montrous wolf of Norse mythology).
In the original serial, the Ancient One was powerless to act in the face of faith. In order to induce the Ancient One to destroy Fenris, the Seventh Doctor is forced to brutally destroy his companion Ace's faith in him. Orman takes this moment in the serial as the starting point for her story. In Orman's alternate version, the Ancient One attacks the Doctor, rather than Fenris, making the Doctor its puppet and ushering in thirteen years of Haemovore control over the Earth. The Doctor, under the control of the Ancient One, is forcibly fed human blood, so that the Ancient One can feed on him. The cycle only ends when Ace, finally understanding why the Doctor betrayed her trust thirteen years earlier, kills him in order to destroy the Ancient One.