Last Signal

Halcyon Relay sits on the frozen plain of Triton, Neptune's largest moon, four light-hours from Earth. For eleven years it passed messages between the inner planets and the probes beyond. Three years ago every transmission from Earth stopped in the middle of a sentence. The crew went home on the last supply ship. Mara Iven stayed.

She keeps the dishes turning, logs the silence every night and rations what the ship left behind. Her only company is ORRA, the station's maintenance system, which has started to repeat itself: the same weather report twice, the same greeting an hour apart.

Then the array catches a signal from the direction of Earth. It is Mara's voice. It describes, minute by minute, what she will do tomorrow, and begs her not to reply. The next day, everything it described happens.

Every message takes four hours to arrive, and four more for an answer to come back. Mara has to decide whether the voice is a warning, a trap, or proof that she is no longer the only version of herself out here, and what it will cost to answer.

Each episode ends on a message sent and opens four hours later, when the reply lands. The delay is the clock the whole series runs on.

Nothing travels faster than light. Every conversation with home takes eight hours, so no one on Triton can interrupt, argue or take anything back.