One day the sun will fail. The fuel powering its nuclear fusion will run out, the sky will grow cold and, if Earth survives at all, humankind will be plunged into perpetual winter. To stay alive, our descendants will need to make alternative arrangements. They will first exhaust the resources of Earth, then the solar system, and eventually all the stars in all the galaxies in the visible universe. With nothing left to burn, they will surely cast their gaze on the only remaining store of energy: black holes. Might they be able to harvest this energy and save civilization?