This teaser for this episode is very short, only about a minute, but it does pretty much set up the premise for this episode. You first hear the warning buoy, but then you actually see it. But unfortunately you only hear sounds of what happened to the warning buoy, but you get the idea of what happened to it. It sounded to me, like someone crunched together a sheet of aluminum foil!

In the first act, we transition to the Starfleet destroyer U.S.S. Justice when it encounters the area where a Starfleet warning buoy was supposed to be, but has been destroyed. Viewers get a history lesson from the science officer and the android character, Lieutenant Enigma, on the bridge, that it was left as a navigational warning: the Doomsday device that was encountered by the Enterprise and the Constellation was in the vicinity, although it was supposed to be inert!

In the next two acts, the captain of the Justice decides to locate the Doomsday device and destroy it, to the objections of the science officer who gave us the history lesson. He points out to the captain that it took two Constitution-class vessels to disable the Doomsday device the first time, and that the Justice is just a destroyer which could not possibly destroy it. The captain ignores this warning and decides to pursue it anyway. He relays a message to Starfleet Command and advises them of the situation, so Starfleet sends another Starfleet vessel to assist, but it will not arrive for a few days.

The crew of the Justice finds the Doomsday device and fires upon it to no avail. The Doomsday device fires back and damages the destroyer, which injures the first officer, leaving him unconscious. The captain orders the phasers fired again, to no avail, and this time when the Doomsday machine fires back, the captain is injured. While losing consciousness, he orders the ship to be blown up as it is maneuvered into the Doomsday device like before. The captain is taken to Sickbay, so the science officer on the bridge takes command of the ship. Lieutenant Enigma objects per regulations and advises the science officer that the chief engineer is the next officer in the chain of command. After objecting to her interpretation of the regulation, the science officer finally agrees and calls for the chief engineer to come to the bridge.

The chief engineer, who appears to be the lead character in many ways, goes to the bridge and is apprised of the situation by the science officer. The chief engineer takes command to the science officer’s chagrin. The science officer asks if the chief engineer is going to sacrifice the ship per the captain’s orders. The chief engineer declines, and reports that the ship has lost too much power to be effective to kill the Doomsday device.

Together, they come up with a plan to lead the Doomsday device towards the nearest star. At a certain distance, the Justice will fire a photon torpedo into the star, causing a solar flare to destroy the Doomsday device. They implement the plan which works as predicted, and the solar flare blows up the Doomsday device. A shockwave shakes the ship again and disables its power, while another larger shock wave is coming towards them!

The chief engineer goes over to a console and gets the power back up where as the science officer hits the engage button. The ship takes off and avoids the shockwave. Later, the captain sits up in Sickbay and appears to be fine. The science officer that wanted control of the ship earlier now has the conn, and the chief engineer is back in engineering, happy that the captain finally called him by name.

When I started watching this episode, I decided that in many ways the episode really doesn’t work right. It was evidently filmed in a small room because of the echoing, hollow sound of the actors’ voices. The dialog is barely rehearsed; the actors hesitate sometimes when they speak, making sure that they get their lines right. The scenes were shot in front of a blue screen; their body outlines are quite evident. The android character, Enigma, was a knock-off of one of the androids from "I, Mudd." Also when the characters want to communicate with their fellow crew members, they tap their Starfleet emblem on their chest. This type of communicator was not used until much later in the Star Trek universe. (This really bugs me somewhat.) Amusingly enough, the captain’s wig keeps falling back a little, revealing his natural dark hair. These are the sort of things that distract a viewer from enjoying an episode. What does work though are the special effects of the ship and space. Even though computer-generated, they do have nice special effects, especially with the U.S.S. Justice and the Doomsday device. They really did a good job of duplicating the Doomsday device.