- "I know you gentlemen have been through a lot, but when you find the time, I'd rather not spend the rest of this winter TIED TO THIS FUCKING COUCH!"
- ― Garry after being proven human
Through an unknown event sometime in 1972 he met George Bennings who he would be friends with for ten years to come.
During the winter of 1982, a pair of Norwegians chased a shape-shifting extraterrestrial organism (imitating an Alaskan Malamute) from their ruined research station to U.S. Outpost 31. Unable to understand the rifle-wielding man's warnings, the American crew mistake his actions for hostility and he is shot dead by Garry. Unknowingly, the crew adopted the dog and Garry orders radio operator Windows to relay news of the attack to McMurdo Station, despite severe radio interference caused by an oncoming storm.
Garry is cynical about Dr. Copper's intention to bring aid to the Norwegian camp and is present when the remains of a Norwegian Thing they brought back are laid out in the lab. During the night, he is awoken by a fire alarm triggered by MacReady and proceeds to the dog kennels to discover what the source of the disturbance is. Along with the other men, he witnesses the dog-thing assimilating the outpost's sled dogs and opens fire on it with his revolver to no avail. After the creature is incinerated by Childs, Garry is present at the autopsy of its charred remains. After performing tests on the organism, Dr. Copper decides to lock its remains in the storage room and after providing Windows with his set of keys, Garry (along with the other men) is drawn outside by the discovery of a half-assimilated Bennings, who is promptly incinerated. Understandably confused by what was happening to his friend, he reluctantly aids MacReady in destroying the rest of it.Mid-way through the film, Garry assists the other men in overpowering a revolver-wielding Blair, who has destroyed the outpost's helicopter, snowcat, radio and killed the remaining sled dogs, under the pretences of preventing the Thing from escaping. After locking him in the tool shed, the men return to the infirmary to find the blood locker open and its contents destroyed - preventing a possible blood serum test. As the holder of the keys, Garry is accused along with Dr. Copper and paranoia breaks out. Possibly realising that he himself dropped the keys after encountering the Bennings-Thing, Windows flees and acquires a shotgun to arm himself. Garry threatens him at gunpoint to let go of the weapon and the paranoid man complies. His authority shattered beyond repair, Garry decides to hand over his revolver and leadership to someone else - giving the men his word that he did not touch the blood supply. Along with Copper and Clark he is taken to the rec room, drugged with morphine and tied to the couch.
In a bid to determine the identity of the remaining crew, MacReady improvises a rudimentary blood-test involving a heated copper wire and samples taken from the men. Still tied, Garry cynically replies that the test is ridiculous and won't prove anything. MacReady decides to test Garry last, taking his hostility as further confirmation that he is an imposter. Dipping the heated wire into the petri dish containing Palmer's blood, the organism unexpectedly reacts, jumping out of the dish with a shriek and revealing Palmer to be a Thing. Noticing the convulsing Palmer-Thing tied up alongside him, Garry and the others begin to panic and shout. The creature sheds its bonds and fatally mauls Windows before being burnt and destroyed by MacReady. Following the chaos, Nauls assists MacReady in finishing the tests, concluding with Garry's, which harmlessly fizzles upon contact, proving his humanity. Tired and frustrated, he demands that the men release him, yelling that he is not willing to spend the entire winter tied up on a couch.The surviving crew set out to the tool shed in order to administer the test to the incarcerated Blair, only to find that he has escaped by tunnelling his way underground. They follow the path and discover that not only had Blair been assimilated, but he had been constructing a small flying vehicle of alien design underneath the tool shed. After the facility loses power, MacReady realizes that the creature now wants to freeze again so a future rescue team will find it. The remaining crew acknowledge that they will not survive and set about destroying the facility in hopes of killing the creature. While setting explosives in the outpost's underground generator room, Garry is attacked and assimilated by the Blair-Thing as he stops to fix his flickering flash-light. Pressing him against the wall, it sinks its fingers into his face - fusing the two together and beginning to assimilate him. He is last seen being dragged off screen by his hideously stretched facial tissue.
Although his death is not shown on-screen, it is certain that Garry is dead, since assimilation meant certain death (although not necessarily immediately). Also, before a Garry-Thing could be produced from the Blair-Thing, the base was destroyed, certainly killing both the human Garry and eliminating any possibility of a Garry-Thing. Regardless, Garry's sacrifice prevented any possibility of the Thing reaching and destroying civilization.
As the Commander of Outpost 31, Garry had a serious and no-nonsense attitude, making him a very adequate leader for a large group of men on a single base in the middle of nowhere in Antarctica. When the Bennings-Thing was discovered and killed, Garry was left shocked, as he had known Bennings for a long time. After everyone became suspicious of him, Garry became a lot more short tempered and willingly handed over his role as leader to any taker, which wound up being MacReady, someone he openly distrusted until the end of the film when the four survivors, including Garry himself, learned they would have to work together and most likely die if they wanted to stop the Thing, a sacrifice Garry was bravely willing to make.
- Garry carries a .357 magnum Colt Trooper Mark III revolver as his on duty sidearm, which he later gave to MacReady because he did not feel up to being in charge.
- According to the character, Garry has been friends with George Bennings for ten years.
- In the short story on which The Thing is based (Who Goes There?), the character Garry is revealed to be an imposter.
- It is believed Donald Moffat improvised shouting his famous line about being tied to the couch, as the line itself is in lower case with no exclamation mark at the end in the original script. This rumour is unconfirmed.