Sent by the Humanx Commonwealth Science Council, a team of explorers manage to find the planet Quofum—which only occasionally appears on long range scans.
The three remaining scientists fall into a survivor's depression realizing their small expedition won't be missed while also lacking a means to return home on their own.
The ancient race (unnamed, but obviously the Xunca) that once inhabited Quofum altered their planet when they realized the inter-galactic Great Evil was eventually coming to their corner of the universe.
Although supposedly starting in 555 A.A. in the Commonwealth timeline, and before the events to be revealed in Flinx Transcendent, the actual amount of time spent by the scientists exploring inside Quofum is unclear.
While implied that the trio spent years investigating the extent of Quofum's mysterious inner workings, this would seemingly contradict the established Commonwealth timeline.