The Outer Limits1963

Trent:
Explain the gold medallions to me.

Breech:
The time mirror works safely only one way; coming into the past from the future.

Trent:
And when the medallions are pulled off?

Breech:
They're focusing elements for the mirror. It's... it's-it's as if time were a rubber band, and you were on one end stretched out tight. As long as the medallion's present, the band stays tight. But when you rip it off, we snap back up to the future.

Trent:
I'm wearing one. That makes me vulnerable?

Breech:
Yes, you're vulnerable. And we'll get you. We'll have to get you, finally. If you kill me, another will take my place. And if you kill him, another.