how much plot stealing is fair game.
Often plots bare more then casual resemblance to something you've seen before. So the question is how much is to much?
For example (this plot would be public domain) what if you had three guys led by a grate hero holding a bridge against an enemy hoard while the rest of the company destroy the bridge behind him?
Been: Somewhere unimpressive, Done?...not so much!
If you can fill the unforgiving minute with 60 sec. worth of distance run,
Yours is the Earth and everything that's in it,
And - which is more, you'll be a Man my son! - RK