Another in what will become a long, long series of ship-in-danger scenarios. Many such episodes end up turning on a magical tech solution. This one saves the tech for saving the captain, and uses plotting to lead to the main solution. This is much preferred to the other way, but it still leaves something to be desired.
Killing the guest star so early is risky business when the episode has been so thoroughly built around his character. But this risk pays off because Kirk learns from it as he mourns. Shatner's face in the first scenes of Act IV convey so much more than the dialogue could. Spock's line offering condolences is almost required by Kirk's reaction.
William Windom is a mixed bag. His early scenes, which convey a sense of clumsy despair, contrast distinctly with the later scenes of his command of the Enterprise. There is little time in the script for his recovery from what he has witnessed, and this works against the actor. Ultimately, he is redeemed by a superb scene in the shuttlecraft. His character is rendered complex enough to be plausible.
A weakness in the episode is the unfortunately bland design of the planet killer. This was certainly due to budget issues, but imagination doesn't necessarily cost more. The creative use of small plastic off-the-shelf Enterprise models (afflicted by lighters) demonstrates that principle well. In fact, the shots of the battle-damaged Constellation, and the shots of both ships, are highly effective. If only the episode's enemy didn't look like a gigantic Bugle chip.
A major weakness in the script is the heavy-handed use of the H-bomb parallel. Typically, social issues are handled with so much more subtlety on Star Trek. This script hits you over the head twice, even though the parallel is somewhat strained. It does reflect the atmosphere in which the show was made, and can be fairly described as bold for its time. But a lighter touch would have allowed it to age better.
And again there is a cutesy ending which can only be the work of Gene Coon. I know there are those who laud his efforts to propel Star Trek to new heights. But it must also be admitted that his little "script lighteners" always seem to distract from the tone of the episode. Once aware of them, they stick out like sore thumbs. This episode is a tragedy, and tacking a lame joke onto the end is a cop out.
Rating: Middle-lower (5)