Back in the late 60s and into the 70s, there was a lot of upheaval in western society...particularly the United States. Some of it was due to the Vietnam War, some to the hippies, some to various other counter-culture causes....there was just a LOT of uncertainly and splintering in the country. The thing history books about this period often omit or only talk about briefly are the various terrorist organizations which thought that demonstrations and voting weren't enough...violence was the means to change. Groups like the Weathermen, the Symbionese Liberation Army, and Puerto Rican separatists (among other groups) were often violent...making bombs, stealing weapons and attacking the authorities. This is the context for the episode.
When the story begins, a Marine and his girlfriend are talking out on the edge of the base...among the trees. Suddenly, two thieves appear bearing military assault weapons they just stole....and they try to kill the couple for spotting them. The lady escapes while her Marine boyfriend takes on the baddies...and is brutally stabbed. He is near death when the FBI take on the case. Eventually they realize that the guns weren't stolen by any terrorist group...but a mercenary (Glenn Corbett) who is looking to sell them to the highest bidder!
As I said, the context for this makes the episode believable and interesting. The story is interesting and even gives you a chance to see a young Diane Keaton and the mercenary's worried girlfriend. Well worth your time and very well made.