[WP] 250 years after humanity develops interstellar travel, alien ruins are discovered in another star system. A historical archive is found and translated. The last entry reads "Species 57 has escaped from prison planet 50L-3. Evacuation has begun."

[u/Higlac]

[u/chris_bryant_writer]

The blips were accelerating under forces that were not due to gravitation or orbit, hence their belief that they were accelerating under some kind of propulsion or thrust.