Balance of Terror - Plot

Plot

The starship USS Enterprise under the command of Captain James T. Kirk is inspecting a line of manned Federation outposts, only to find they are being destroyed by an unknown enemy. The latest to fall is Outpost 4 near the Romulan neutral zone. Lieutenant Commander Spock explains that the neutral zone came into being following the Earth-Romulan War treaty a century earlier. Due to the lack of use of visual communications, the two races have never seen each other and only communicated over subspace radio. Kirk fears the Romulans are preparing for another war.

Kirk discovers that the attacker is a lone Romulan Bird of Prey equipped with a cloaking device. The cloak is not perfect; the Enterprise can track the ship, which is returning home to report on weaknesses in the Federation's defenses. The Enterprise taps into the Romulans' internal security camera, revealing that the Romulans appear identical to Vulcans. Lieutenant Stiles, who had family fight and die in the Earth-Romulan War, begins to suspect the Vulcan Spock of treason.

During a briefing over the Romulan ship's capabilities, Stiles suggests the Enterprise attack the Romulan vessel before it can reach the Neutral Zone. Spock agrees with Stiles' suggestion, believing the Romulans are likely an offshoot of the Vulcans from their age of savage warfare before the discipline of logic took hold. Spock reasons that if the Romulans retained Vulcan's pre-logic martial philosophy, they would surely infer weakness in the lack of response from the Federation and launch a full-scale war.

A cat-and-mouse game ensues, with each ship having its strengths and weaknesses. The Enterprise is faster and more maneuverable, while the Romulan ship has the cloaking device and an arsenal of immensely destructive plasma torpedoes, but their range is limited and firing them requires so much power that the ship must decloak temporarily. The two commanders are soon locked in a battle of wits; at one point the Romulan commander refers to Kirk as a "sorcerer" who can read his thoughts.

In the final act the Romulans, almost beaten, dump a nuclear weapon along with other debris in hope that the Enterprise will get near enough to the weapon to be destroyed. However, Kirk suspects a trap and orders a point-blank phaser shot that detonates the bomb. The Enterprise is badly shaken by the blast; Kirk decides to use this to his advantage, ordering operations to work at minimal power to exaggerate the apparent damage. Although the Romulan ship's fuel is running low, a member of the crew with connections to the Romulan praetor convinces his commander to finish off a seemingly helpless Enterprise. When the Romulan ship decloaks to launch a torpedo, Kirk tries to spring his trap, but an equipment failure leaves the phasers off-line and Mr. Stiles incapacitated. Spock rescues Stiles and fires the phasers in time for the Enterprise to disable the Romulan ship.

Kirk hails the crippled vessel and at last communicates directly with his counterpart, offering to beam aboard the survivors. The Romulan commander declines, saying that it is "not our way" to accept such assistance. The commander expresses regret that he and Kirk live in the way that they do, pointing out that "In a different reality, I could have called you friend." Then, with "one more duty to perform," the commander triggers his ship's self-destruct, preventing its crew and technology from falling into Federation hands.