I like this movie, but the one thing that really bugs me is how the scientists could be dumb enough to believe that Exeter and all the others share the exact same abnormality, which clearly doesn't look human.
First, don't forget that Exeter and Brack put all the other Club members under their dreaded "sun lamp." Even if they were inclined to question Exeter's origin, they were now conditioned to obey Exeter's orders without question. Ruth, Steve, Adolf Engelborg, and finally Cal were the only scientists spared.
So why didn't one of them twig right away?
Well, would you necessarily expect your host to be non-human? Put yourselves in Cal's place, or Ruth's and Steve's. They're not going to think of the ET angle first. Not for a LONG while.
But Cal gets his first clue, when Exeter blows the gaffe on the Mozart question.
CAL: And how does Mozart impress you, Exeter?
EXETER: I don't know the gent--ah. My mind was wondering. Your composer, of course.
YOUR composer?!? Cal "gets it," and that's why he abruptly excuses himself and summons Ruth and Steve to tag along with him.
It was the 1950s, everyone looked weird back then.
You just killed my girlfriend.....thats actually....kinda pissing me off....huh....
People look more weird today.
Since this took place in the 'Cold War 50's', I was surprised that they didn't suspect that Exeter and Brack might be communists.