- "I don't know what the hell's in there, but it's weird and pissed off whatever it is."
- ― Clark to MacReady
Clark was a dog handler stationed at American Antarctic research station, U.S. Outpost 31. The character appears in the 1982 film The Thing and was portrayed by actor Richard Masur. His fate is also briefly touched upon in the 1991 comic series The Thing From Another World.
During the winter of 1982, Clark and the rest of the crew witnessed two Norwegians chasing an Alaskan Malamute towards the outpost in a helicopter. The pilot was killed when he accidentally dropped a grenade and the passenger was shot dead by station commander Garry, who thought that he was hostile. The crew adopted the dog afterwards.
That evening, Bennings requested Clark to put the dog in the kennel. Later, Clark heard strange noises from the kennel, where two sled dogs quickly fled in panic and he saw an unknown creature assimilating the other dogs. He quickly headed back to warn the others and they all confronted the Kennel-Thing. R.J. MacReady and the others fired guns at it in an attempt to kill it to no avail, before Childs arrived with a flamethrower and MacReady ordered him to incinerate it.
Later, Blair, who is suffering a mental breakdown, begins to destroy the radio. Childs tells the others that Blair also destroyed the helicopters, tractor and radio with an axe, and killed the remaining sled dogs. After hearing this, Clark rushes to the kennel only to find them already axed to death. Paranoia quickly sets in as the first attempt to develop a test using uncontaminated blood samples is sabotaged by an unknown party.
Clark is one of the main suspects of being assimilated as he spent a lot of time with the infected dog earlier. Blair warns MacReady specifically about Clark when he is imprisoned in the tool shed. MacReady is ready to watch Clark carefully as he is discussing about the next course of action with the others. Clark is tied and drugged in the recreation room alongside Copper and Garry.
Clark and the others begin to suspect MacReady is infected when a scrap of torn shirt containing his name tag is found at the camp, and locked him outside in a severe blizzard. Somehow finding his way back to camp without a guide line, MacReady breaks into a storage room and threatens the rest of the crew with dynamite.
In the course of the standoff, Norris suffers a heart attack. When Copper attempts to revive him by defibrillation, Norris' body transforms and bites off Copper's arms and he bleeds to death. As MacReady burns the Norris-Thing. Norris' head detaches from the body and tries to escape as the men put out the fire, but the head is discovered and incinerated as well.
MacReady proposed a test on everyone to tell who is human and who is a replica. Clark, in an act of mutiny, tries to stab MacReady with a scalpel (he took him in the infirmary during the crisis with Norris), but is quickly shot in the head and killed by MacReady in self-defense. The rest of the crew complies with the test; blood samples are drawn from each member of the team including Copper and Clark and jabbed with a hot wire to see whose blood will react defensively. Upon realizing that Clark was not infected, Childs denounces MacReady as a murderer.
Clark was a very quiet and serious man. He was shown to care deeply for the sled dogs, as during the Kennel-Thing encounter he interrupts the other members by grabbing their shotguns when they shoot the assimilated dogs and later goes back to the kennel and finds the dead bodies of the sled dogs in sadness that were unscathed by the Thing but were killed by Blair. Due to his self-preserved nature and the fact he spent a lot of time with the assimilated dog, Clark was one of the primary suspects, but he retained an unusually calm and collected attitude up until he finally had a violent burst and tried to stab MacReady.
- Clark is the only U.S. Outpost 31 crew member to be killed by a human (MacReady).
- In Who Goes There?, unlike the film, Clark actually turns out to be assimilated by The Thing.
- Clark was used as a red herring in the movie (for example Blair warns MacReady about Clark specifically, Garry asks about Clark as the first person after finding of the destroyed blood, and in a deleted scene, Clark's name was called by Bennings when he entered the station, spotting a mysterious man which is likely Palmer or Norris).