Dek (Dimitrius Schuster-Koloamatangi) is a juvenile Yautja denied entry into adulthood by his disapproving father. Dek is a "runt" and a disappointment to the clan.
Dek vows to prove himself in the most ostentatious way: to hunt and kill the Kalisk, the apex predator of the death world Genna where everything hunts everything else. The Kalisk has never been taken as a trophy.
The Weyland-Yutani corporation has an expedition on Genna entirely composed of Synths: humans would simply not survive. Nonetheless things have not been going smoothly to say the least.
Dek encounters the heavily damaged, abandoned Synth Thia (Elle Fanning) who claims to have encountered the Kalisk. Much as Yautja hunt alone Dek decides Thia can be used, like a tool, in his hunt.
Shenanigans ensue