Iron Lung

The Quiet Rapture took everything. Stars, colonies, habitable worlds — gone without explanation, leaving humanity compressed onto surviving space stations with no map home. Simon, a former operative imprisoned for the destruction of a space station he maintains he had no part in, is offered a deal: pilot the SM-13 into the blood ocean on moon AT-5, retrieve a sample from a massive skeletal structure detected at the floor, come back alive. The submarine is nicknamed the Iron Lung. It is a small, sealed thing. He descends.

The first images from the ocean floor show a figure — enormous, skeletal — half-buried in the sediment. Mission control orders him up, then orders him back down to collect a physical sample. The turnaround is too fast. Simon starts noticing what he wasn't supposed to: the camera mounted in the vessel isn't recording — it's an X-ray device, irradiating him with every minute he spends inside. He finds audio logs from SM-8, a vessel that supposedly never launched. He was not the first.

Blood and organic matter begin seeping into the submarine. The life support degrades. Carbon dioxide levels rise. Simon starts hearing a voice that speaks of a light beneath the ocean — something vast and beckoning, something that the previous pilots heard too, in their final logs. The mission coordinator Ava stays calm on the radio. Her calm stops reading as reassuring.

Simon retrieves SM-8's data and pieces together what the ocean is: not alien, not ancient. The blood is the congealed remnants of humanity — billions of dead, compressed and dissolved into a collective, slowly forming a hive mind. The creatures moving through it are not monsters. They are what people become here, drawn toward something enormous at the bottom that the organization running these expeditions has been trying to reach for thirteen missions. They have been sending people to feed it.

Simon does not surface. With the hull filling with organic matter and rescue impossible, he tapes the black box data to a life vest and releases it into the ocean above him. Then he sabotages the Iron Lung. The vessel implodes under pressure at the same moment a massive shape closes in from below. A transmission from command acknowledges a "successful harvest." The final image is moon AT-5 beginning to bleed into the surrounding vacuum of space.