The Tain is a 2002 novella by urban fantasy author China Miéville, reprinted in his collection Looking for Jake.
In "The Tain", the "fauna of mirrors" have escaped into the human world seeking vengeance. They were forced to take human form whenever a human appeared in a mirror. Now, disembodied lips and hands, along with other, more complete "imagos" are attempting to wipe out the humans who imprisoned them in mirrors.
The story is told from two points of view: firstly, that of a human survivor who has become immune to the vampire-like imagos and secondly from one of the imagos, who tries to persuade the reader to be sympathetic to the prior plight of his kind. The aim for our human hero is to reach the primary Tain representative on Earth, the Borgian "Fish of the Mirror," who has situated himself in the British Museum. The novella ends with a twist which leaves humanity's future in doubt but also offers the remaining humans a chance of salvation.