Palimpsest

by Charles Stross

Pierce is a police officer with the Stasis, a special institution dedicated to the preservation of humanity by its agents who are able to travel through time. After every extinction event resulting in humanity's end, the Stasis reseeds Earth with a replacement group of humans time-jumped from an earlier era. However, the Opposition, an organisation that seems to struggle against the Stasis, has been created over time, and it seems that Pierce is somehow tied to it.