The Exact Moment Each Person Became Assimilated In The Thing

While the audience might have a ton of emotional investment in McReady, it's Blair that acts as the films guiding force of reason up until his rapid descent into madness. It's his research that informs the team about how The Thing assimilates people, and what would happen should it make it back to civilization.

It's this knowledge that causes Blair's erratic behavior as his sabotage of the helicopter and radio equipment is done to prevent The Thing from escaping to the mainland. Yet in a shocking turn, when the group comes to test the blood of Blair, it's revealed that he's not only disappeared but has been building a spacecraft!

So the question remains, when did Blair become infected? In between his personal lockdown, two days are said to pass, with the group bringing him food and monitoring his activity. As we know that Norris and Palmer are assimilated at this point, it's not unreasonable to assume they approached Blair and infected him at some point.

However, if you're looking for on-screen evidence, look no further than the autopsy scene, which explicitly shows Blair touch The Thing's body with a medical device before PLACING IT TO HIS LIPS. For a man who detailed the single-cell infection, not a smart move right?