At Meridian, a research station at the top of the world, station doctor Ren is woken at 3 a.m.: a crew member has walked out into the dark. The investigation uncovers that the station clock is running forty-seven days fast and the security footage is looped. And on the horizon, a sun-sized light pulses in prime numbers, drawing closer since December - learning what morning looks like from the crew's own routines, their floodlights, and finally Ren's heartbeat.