A long leech-shaped object with a glowing center slices, dices, and eats planets!
The conflicts are between two ships and said object, and (more interestingly) members of the crew and Commodore Decker.
Highlights:
most of Decker’s performance
Spock’s performance
interpersonal conflict
ending – nicely dramatic
Lowlights:
battle scene(s) conflict
Decker’s ending overacting
Spockism: “Vulcans never bluff.”