Earth Colony Ship 4 was supposed to arrive at its new world in about twelve lifetimes. Accounting for inertial drift, getting knocked off-course by space debris, and whatever the event was, the investigators figure it got about two-thirds of the way there.
The robot probes from Gaia-8 nearly missed it, because the majority of their scans were for lifeforms, or at least carbon masses that used to be lifeforms. Colony Ship 4 has none. Not so much as a carrot stick forgotten at the bottom of a food storage unit. No humans, no livestock, no pets, no garden plants, nothing. Every last scrap of organic material has been stripped. Even items like leather shoes and cotton clothes are missing.
What's not missing is evidence. There's plenty of that. The robots were able to sample enough to confirm several things. The stains found all over the bridge, engineering, and the arboretum? The rumours are true. It's from human blood. Whatever happened, it was violent.
The story about the DNA catalogue is true as well. There's one signature that doesn't match any known species, and no-one's been able to piece out what organism owns the genes because... they're not quite genes, and the sequence isn't quite DNA. It doesn't match the genome structures of local life on Gaia 8 either.
As absolute as the removal of all organics was, the ship itself was left completely intact. Those spooky shots of Ship 4 drifting in space with all the interior lights on are not from a special effects rig. One of the robots took video of a bathroom tap left on, water endlessly running, going down the drain, and filtering through the grey-water recycling, working perfectly. You'd expect a bloodstain to be nearby, but there's not. Instead the closest one is three hatchways down, inside a utility closet. As if the sound of the running water was meant as a decoy but ultimately failed.
Elsewhere, on the residential decks, the robots found music and video players still playing. Education screens stuck on quiz question #5. Plates with all the food removed, but still in cooker modules.
Back on the bridge, a sign that some of the crew at least had had time to react. The cover of the communications panel pulled off and discarded on the floor, several bootprints visible on it. The clear shielding set over the controls. And a single, text-only message, obviously composed with the understanding that no other colony ships would receive it until they reached the end of their own voyages and sent their arrival signal:
STOP TRANSMITTING NOW OR ELSE THEY'LL FIND YOU TOO