We're back to some overwhelmingly grim tidings with this episode, a jarring reminder that there are some very dangerous threats out there in space. In a way, this can be looked upon as a precursor to the entire Borg threat introduced on the TNG series; on that show, something like the Borg was needed to shake the Enterprise and the Federation out of their complacency - or, shake them to the core, as is done to Commodore Decker here. The actor, Windom, may very well have ended up with the single best performance, as Decker, during the run of the original series. His loss is almost unimaginable - his entire crew is dead, thanks to one wrong move on his part. He's a walking dead man during the course of this episode - it's easy to compare his character to Ahab from the famous 'Moby Dick' novel, and the monstrous killing machine here to the white whale. But, Windom brings something more to the part. He's compelling from start to finish and adds such startling nuances to an already deeply fascinating, dark character. Picture Kirk as slightly older, not so sure of himself anymore; add on devastating trauma and then complex psychosis composed of guilt, obsession, and suicidal feelings - Windom juggled all of these and more to great dramatic effect.
The cosmic threat of this huge alien weapon, while exciting in itself, takes on a much more darker tone thanks to the presence of Decker on the bridge of the Enterprise. The whole plot seems to take a back seat, for awhile at least, to the strange, awful relationship between our psycho-damaged commodore and this unfeeling machine. Everyone else becomes an incidental side player to the conflict between these two, but, of course, it's Decker, in his insanity, who creates a relationship; he no longer sees it as just a machine, a programmed robot, but as his personal devil. And one definition of insanity is trying the same thing over & over, expecting different results, such as phasers penetrating impenetrable Neutronium. He looks around his new bridge, replacing the one he lost on the Constellation, and sees only tools for his use. It's one of many great moments throughout, and usually on that bridge. The entire episode seems to have benefited from everyone giving an extra effort - from the ruined exterior and interior of the sister starship to that good fight scene between Decker and the security officer (it appeared as if they really tried to suggest a futuristic style of martial arts not seen before). The writing, direction and editing are all top notch. Not to mention, Windom, as Decker, ends up with probably the best death scene of the entire series.
