Although NBC aired this as the first episode, it's not the pilot. That's why the end theme music (which is what was used for almost all of the 82 episodes) is complete. The pilot was actually "Affair in T'Sien Cha" with Vera Miles, which aired as the 14th episode.
The network was right to show this first, because "So Long Patrick Henry" does a much better job introducing the premise and the characters: plainclothes Pentagon agents Kelly Robinson and Alexander Scott (played by Robert Culp and Bill Cosby). At the start of the series, it's stated that these men have already been teamed up for over a year.
Guest stars: Ivan Dixon, Cicely Tyson, James Hong, Richard Loo, and Nick Colasanto.