Particularly in anthology series such as "The Twilight Zone" and "The Outer Limits," story is everything. In the case of "The Invisibles," writer-producer Joseph Stefano (who also wrote the screenplay for the Hitchcock classic "Psycho") weaves a spellbinding plot of aliens, political intrigue, and plot twists.
The hero, played by Don Gordon, is GIA Agent 021 (three times as good as 007, get it?) who poses as a social outcast so as to be recruited by the Invisibles. His mission is to bring them down from within, but he learns only too late that they are onto him and are hoping to use him to infiltrate the GIA. The acting and special effects are above-average for this series, but the story itself is what sets this episode apart. In less skilled hands, the story could have quickly degenerated into convoluted, preposterous slop. However, Stefano was the series' best writer (with the possible exception of Harlan Ellison, who penned far fewer episodes), and he handled the plot masterfully. If you've never seen an "Outer Limits," either "The Invisibles" or Ellison's "Soldier" would be the place to start.