Review of The Tenth Level

I saw this movie when I was 13 years old. I have not seen it since, but to this day, the movie keeps me emotionally gripped whenever I think about it. It well demonstrates what man is capable of doing to another man if pressured enough. William Shatner is absolutely, devilishly brilliant as the menacing doctor. I would love to see this movie again, so if someone knows how I may obtain a copy I would be terribly grateful.