John Carpenter’s The Thing follows a group of American researchers in Antarctica who encounter a parasitic extraterrestrial life-form that assimilates and imitates other organisms. Paranoia kicks in and the group find themselves living a nightmare in the middle of nowhere, and unsure if they can trust the people they live with.

The Thing, some with more screen time than others, but all of them have been under the microscope for decades, as the film left a big question that fans are still trying to find the answer to.

Related: Why Michael Myers Isn't In Halloween 3

When the team learned that the creature didn’t need much time to assimilate an organism, Copper suggested they all took a blood test so they could compare it to the samples they had in storage. Once they got there, the blood supplies had been destroyed, and they never learned who did it. Garry was in charge of keeping the keys, and Copper was the only one who had constant access to them. The team who were on the spot when Copper suggested the blood test were Childs, Garry, Fuchs, and MacReady, with Blair locked in the shed, Clark with his dead dogs, Nauls probably in his own area, and Windows recovering from his recent beating, somewhere. None of them were Things at the time, and the only ones not on the spot that were later revealed to be Things were Norris and Palmer.

Donald Moffat and Kurt Russell in John Carpenter's The Thing

When they found the sabotaged blood it was still dripping, so the attack was recent. Those confirmed to be non-Things at that moment were Garry, Copper, Childs, MacReady, Nauls, and Windows, so there was no reason for them to sabotage the test. It’s unclear when Palmer and Norris assimilated, but it’s possible that one of them picked up the keys after Windows dropped them, destroyed the blood supply, and returned the keys somehow. With this in mind, most fans have pointed their fingers at Palmer, accusing him of the sabotage. This idea is ed by Palmer’s reaction when they discovered the blood, as he remained quiet, and cinematic language, with Palmer being out of focus when Garry stepped down as commander.

Three decades have ed and neither Carpenter nor any cast and crew have offered an answer, and it’s probably for the best – The Thing was all about paranoia and distrust, and the mystery of the sabotaged blood is a big part of that. Still, it’s fun to read some in-depth theories about it, with some of them offering very believable clues and explanations on who did it.

Next: Every Horror Movie Franchise Reboot