Must have been that experience he got from working on
Star Trek!

I always love Gary Lockwood's performance in this great Western.

I thoughtdang, Gary Lockwood is nailing this part!
His range of emotions was far more apparent than he was allowed to display in his follow up film 2001: A Space Odyssey.

I watched the movie again tonight. I got it for my dad on Father's Day because it was one of his favorite westerns, and he let me watch it with him as a kid. I've never forgotten that viewing.
However, I hadn't seen it for a long time, and I never appreciated a lot of it when I saw it as a kid. Firecreek is almost a forerunner to The Wild Bunch in its grit and world-weary tone. I also noticed little details I didn't see before, such as the gang burned their partner who got shot. I never put the firewood, burned chair and ashes together when I was younger. I also thought the direction/cinematography had a bit more creativity to it than standard fare.
But, yeah, as I watched, I thoughtdang, Gary Lockwood is nailing this part! He really did bring a great feeling of menace to the role. I never realized how greasy the whole gang was (even them getting drunk and burning their partner elevates them to an odd level of creepy), apart from Fonda, until I watched it at this age.
My favorite Stewart moment was when he opened the barn and saw Arthur. That little look away/whimper he does was fantastic.
All in all, Firecreek is a classic to me.

Agree. Great perfmances all around in a criminally underrated movie. You never knew which way Lockwood's character was going to jump. Incredibly menacing. Gary did a bang-up job.

I agree. Lockwood played an excellent antagonist here.
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