The most "complete" of all the original cast films and my favorite. This blends a "who done it" mystery with action, aliens, and some deep cold-war introspection in the proposed "peace" between the Klingons and the Federation. For once, each cast member had a key role to play in the story. Bones is important in trying to save a key Klingon, Spock is left in charge, Checkov makes a startling discovery, and Scotty saves the day. Sulu is now Captain Sulu, and he also has an important part to play. There are also some funny moments, like Uhura trying to speak Klingon. This is the most satisfying of the originals because of the interesting and entertaining plots and especially because each cast member had his/her due. The effects were properly placed too and quite well done. The cast was top notch, and included Christopher Plummer as Chang and Michael Dorn as Warf. This had action, intrigue, and political commentary, with a brief look at how Spock and Kirk are almost two halves of a whole. This one was great! As for the cool alien--there is a really hot shape shifter who was interesting.