Star Trek, Balance of Terror. The Enterprise battles a Romulan ship suspected of destroying outposts near the neutral zone. The featured guest star is the late Mark Lenard, and is our first glimpse of what would become an annoyance in the Trek-verse. There had been a war before there was visual subspace communication so neither side were aware of what the other side looked like. I believe that this lore had been broken by subsequent programs but I love the notion. We also get to question Mr. Spock’s loyalty.
The program plays out like a World War Two submarine battle. With the stakes being a full scale war, the Enterprise is the only thing standing in the way of another prolonged conflict, possibly on three sides with the Klingons joining in. Some of the acting is a bot over the top, and the death of just one crewman… the young officer who was getting married in the opening of the program is a bit much, but I still love this episode. If I could only watch one episode of the original series again it would be Balance of Terror.