10 Small Details That Make John Carpenter's The Thing Perfect
8. The Broken Seal
The couch scene in The Thing is one of the most tension-filled few minutes in the film. Watching MacReady work his way through the blood samples, one by one, is nail biting - and that jump that comes has knocked more than one person off their seats.
Why did it happen? As they surmise, each individual cell of the creature can be a unique and separate being, one that wants to defend itself. They settle on blood tests, comparing uncontaminated blood to test who is human. Except the creature is one step ahead.
They find that the blood stored in the lab has been destroyed. Immediately, they fall to infighting as, and the creature was aware of this, they assume that the only way for anyone to gain access to the blood is with Garry's or Windows' keys. Under normal circumstances, that would be correct - leading them to believe that one of them has been assimilated.
However, the eagle-eyed can see that the creature engineered this without having to use Garry's keys at all. The seal around the container is broken and, as they have already deduced, a single cell of the creature is an entity in itself. One cell could slip through that gap, destroy the blood and rest in knowing that the humans would naturally blame each other.
There is another theory that states Windows loses his keys when he walks in on Bennings being assimilated, adding another twist to the tale.