Dr. Halvorson was the lead researcher and medical officer at the Norwegian camp, until he was assimilated by the Thing. After Kate Lloyd and American helicopter pilot Sam Carter incinerate the Split Face thing, they notice Sander fleeing from the outpost in one of the snowcats. Deducing his destination, the pair follow the creature to the UFO crash site and attempt to board the ship. Following the activation of the spacecraft, the two become separated, with Kate falling into one of the craft's vents and Carter proceeding through the main hatch. Hearing strange scuttling noises and raising his flamethrower, it is strongly implied that Carter is assimilated by the Sander-Thing off-screen.
After awaking from the fall, Kate wanders the ship until she is suddenly attacked by the Sander-Thing, still using Sander's face on a terrifying alien body. As Kate flees from the creature, its face ripples and tears away, revealing a sickening frenzy of teeth and tentacles as it gives chase. Kate finds sanctuary within a small enclosed area where the Thing cannot reach her and it eventually gives up. Kate frantically crawls for a nearby grenade, as the creature grabs her by the foot and drags her from the hiding space. As Sander-Thing attempts to assimilate her, Kate hurls the grenade into the creature's waiting mouth. It detonates, blowing apart the Sander-Thing and permanently disabling the craft.
- Sander-Thing's long arm on its back is similar to the unused Tongue Centipede-Thing.
- The Sander-Thing's death is similar to how the Blair-Thing was killed. They were both blown up with explosives used by the protagonist.