TOS Season 1 Episode 14 Balance of Terror

Plot

The USS Enterprise, under the command of Captain Kirk, is investigating a loss of communications with a line of Earth outposts near the Romulan Neutral Zone, formed under the terms of the peace treaty that ended the Earth–Romulan War a century earlier. Because there were no visual communications at that time, the two races have never seen each other.
While Kirk officiates at the wedding of Lieutenant Tomlinson and Ensign Martine, Outpost 4 comes under attack. The Enterprise comes to Outpost 4's aid and contacts the base commander, Hansen, who reveals he is the only survivor of an attack by an unknown enemy. As they speak, the enemy ship reappears, fires, and disappears. The shot destroys the outpost and kills Hansen.
The ship's sensors locate the attacker, which remains invisible. Kirk surmises that the attacker is equipped with a cloaking device. A coded message from the intruder provides a view through one of its internal cameras, revealing humanoids with an appearance like Vulcans. Lieutenant Stiles, the navigator, son of a service family that lost several members in the Earth–Romulan War, begins to question the loyalty of the Enterprise's first officer, Mr. Spock.
During a discussion of the Romulan ship's capabilities, Stiles suggests the Enterprise attack before it can reach the Neutral Zone. Spock agrees; he reasons that if the Romulans are in fact an offshoot of the Vulcan species and have retained the martial philosophy of the Vulcans' ancient past, they would surely take advantage of any perceived weakness.
A cat-and-mouse game ensues. The Enterprise is faster and more maneuverable, while the Romulan ship has a cloaking device and immensely destructive plasma torpedoes. However, the range of these torpedoes is limited, and firing one requires so much power that the ship must decloak first.
After several attacks, the Romulans, almost beaten, plant a nuclear weapon amidst jettisoned debris. When Spock detects a "metal-cased object", Kirk orders a point-blank phaser shot that detonates the device. The Enterprise is shaken by the blast and many of the phaser crew are incapacitated, requiring Stiles to fill in. Kirk orders operations to work at minimal power to exaggerate the apparent damage and lure the Romulans in for a kill shot. Although the Romulan commander suspects Kirk's trap, Decius, a politically well-connected member of the command crew, pressures him to attack. When the Romulan ship decloaks to launch a torpedo, Kirk tries to spring his trap, but a coolant leak in the phaser control room incapacitates Stiles and Tomlinson. Spock rescues Stiles and fires the phasers, mortally wounding the Romulan ship.
Kirk hails the Romulans and at last communicates directly with his opponent, offering to beam aboard survivors. The Romulan commander tells Kirk that he regrets having met him in combat, that "You and I are of a kind. In a different reality, I could have called you friend." He declines Kirk's offer to take off his crew, telling the Captain that it is not the Romulan way to be taken prisoner. The Commander then triggers his ship's self-destruct system.
Enterprise's only fatality is Lt. Tomlinson. Kirk goes to the chapel to offer comfort to a grieving Ensign Martine.