Kirk: Matt. Where's your crew?
Decker: On the third planet.
Kirk: There is no third planet!
Decker: Don't you think I know that?!? There was! But not anymore! They called me, they begged me for help! Four hundred of them! I couldn't!! I... I couldn't... [breaks into sobs]
The Enterprise is investigating the destruction of several planetary systems when they come across a crippled starship, the U.S.S Constellation. The only person on board is Commodore Matthew Decker, the ship's captain. Through the disturbed captain's rantings and the pre-recorded Captain's Log, Kirk and co. deduce that after the ship was severely damaged, the entire crew was beamed down to a local planet, the captain taking the duty of going down with the ship after seeing to his crew's safety. However, a planet-destroying weapon constructed long ago by a long-dead race destroyed the very planet where the captain thought his crew would be safe, leaving him alive and grieving. While Kirk, Scotty and a small repair crew stay on board the Constellation, Decker is beamed back with McCoy.
Decker isn't taking Survivor Guilt very well and takes command of the Enterprise upon learning that Spock would rather take logical steps than press forward and destroy the planet killer at all costs. Decker recklessly endangers the crew in his attempts to destroy the thing that killed his own crew. When Kirk finds out about this, he is not amused to say the least. He orders Spock to relieve Decker, but the commodore is only finally removed when Spock threatens to arrest him. Spock sends him to sick bay, but instead of going there he attacks his guard and steals a shuttlecraft, intending to shove it down the machine's gullet — with himself inside.
No one is able to save Decker. He doesn't want to be saved. However, Kirk believes he had the right idea to destroy the device. They just need to use something bigger than a shuttlecraft. Hmmm...this junked up starship that no one's using just might do....
The Doomsday Tropes:
- Abandon Ship: The crew of the Constellation (save for Decker) did this prior to the episode. Unfortunately, not realizing what they were dealing with, they evacuated to a planet that the planet killer then destroyed.
- Absentee Actor: Uhura doesn't appear in this episode, her duties assumed by Lt. Palmer, played by Elizabeth Rogers. Chekov is also absent.
- Asteroid Thicket: A more justified example than most, as it's the remains of a planet that was recently blasted to pieces. There hasn't been enough time for it to either dissipate or coalesce into a new planetoid.
- Beard of Sorrow: It's probably been a few days since the destruction of the crew of the Constellation, as Decker has grown some hefty stubble. His unkempt appearance makes him stand out among the clean and neat members of the Enterprise crew.
- Blatant Lies: An accidental case created by the remastered version. It is stated that other than the bridge, the Constellation is habitable. One look at the huge portions of the primary hull in particular which have been reduced to their structural framework makes that laughably wrong.
- Bottle Episode: All the scenes are filmed on the Enterprise sets, including those on the Constellation (which is of the same class, so of course they'd be designed the same way).
- Captain Obvious: Quite a literal example this time, when Kirk observes that the Constellation was attacked. Really, Jim? You don't think that kind of damage could be accidental?
- Casual Danger Dialog: Kirk is still cool, despite being seconds from being blown apart.Kirk: Gentlemen, I suggest you beam me aboard.
- Catastrophic Countdown: Kirk has 30 seconds to get off the Constellation.
- Damage Control: Despite the severe damage to the Constellation, Scotty the Miracle Worker manages to get the ship moving on impulse, raise the Deflector Shields, and recharge a phaser bank.
- Death Seeker: Decker.
- Doctor's Orders: Discussed. When McCoy protests Decker taking command of the Enterprise, Spock reminds him that he has the authority as Chief Medical Officer to certify the Commodore unfit for duty. McCoy eagerly states he'll certify that right now, only for Spock to point out for it to be valid he will also need to provide medical proof (which McCoy does not have as he has not examined Decker).
- Doomsday Device: Obviously, although any theories about the planet killer's actual origin and purpose remain just that.
- Dull Eyes of Unhappiness: The very first thing we notice about Decker is the "Lord, kill me now!" look in his eyes.
- Due to the Dead: Me TV (who was showing the episodes in order) reran this episode shortly after the death of William Windom.
- Explosive Instrumentation: Nothing says "transporter malfunction" like a couple of smoke-plumed explosions.
- Face Death with Dignity: Decker tries, but he clearly loses it seconds before the end. Kirk does a much better job of it.
- Feed It a Bomb: And 97.835 megatons megatons of fusion energy make for one hell of a bomb.
- First-Name Basis:
- As an old friend, Kirk calls Decker "Matt" when the damage control party first finds him. After he realizes the risk Decker is causing to the Enterprise, he switches to "Commodore" when telling him to give command back to Spock. Later, starting with "Matt, you'll be killed," he goes back to his friend's first name, begging him not to kamikaze the planet killer.
- Decker also does this. When he's first found, he calls Kirk "Jim." Later, though, after taking command of the Enterprise, he calls him "Kirk" or "Captain."
- Forced to Watch: A big part of why Commodore Decker is so traumatized; not only did he beam his crew onto a planet in the machine's path, but he had to listen to them die from his crippled ship.Decker: They called me, they begged me for help, four hundred of them! I couldn't! I-I couldn't! (breaks down in tears)
- General Ripper: Commodore Decker. His goal is fine, but his methods are suicidal... literally, as it turned out.
- Generic Doomsday Villain: A giant cone mindlessly bent on planetary destruction spinning around in space like a forgotten land mine.
- Ghost Extras:
- One of the most decisive aversions of this trope in franchise history. Throughout the episode, as the power struggle between Spock and Decker escalates, the camera routinely cuts to the reactions of the crew members in the "background." None of them have any dialogue, but their facial expressions speak volumes.
- When Spock accepts Kirk's order to relieve Decker of duty and assume command of the Enterprise, Decker (knowing that neither Kirk nor Spock have the authority to relieve him) resists. But then Spock silently gestures to the security redshirts stationed by the turbolift, and they advance forward — ready to subdue Decker by force if necessary, proving that the crew of the ship is behind Spock and will back his play. Spock could have very easily nerve-pinched Decker if he hadn't cooperated, so Spock is going out of his way to demonstrate how important their support (or lack thereof) is in the power struggle.
- Go Look at the Distraction: Kirk uses the Constellation to divert the planet-killer from moving in on the Enterprise.
- Going Down with the Ship: Decker intended to do this. Tragically, however, the planet killer wasn't interested in his ship, so his entire crew was killed while he lived. Decker ends up going down with a shuttlecraft later on.
- Hand Signals: One of the reasons Decker realizes he is fighting a losing battle asserting his authority on the ship is when Spock just has to make a hand gesture and the bridge's security officers eagerly step forward for the word to drag the Commodore out.
- Heroic BSoD: Decker is in the midst of one when he's found on board the Constellation. He has another, major one when he makes his suicide run at the planet killer.
- Idiot Ball:
- No one considers firing into the obvious weak point of the planet killer until Decker completely loses it and flies a shuttle into it, revealing the weakness. Of course, this is equivalent to firing down the barrel of a gun and hoping not to be shot, but it's not like they had many options, especially when it had them in a tractor beam. Star Trek Online actually went with this route, but the player can only cause damage with special, high-powered weapons, not their standard loadout.
- One that happens offscreen is Decker's initial decision to have the crew evacuate to a planet. It was cutting up a planet when the Constellation found it, so they should have considered it would continue doing so. Instead, he fails to consider it would go right back to what it was doing before it engaged his ship, and his entire crew is killed as a result.
- I'm a Doctor, Not a Placeholder:Kirk: Bones, have you ever heard of the Doomsday Machine?
Bones: No, I'm a doctor, not a mechanic.
- Irrevocable Order: Once the self-destruct on the Constellation is triggered, there's no stopping it (apparently because of the ship's damaged condition, with the engines already on the edge of blowing up without any extra nudge in that direction). This causes some consternation when the Enterprise transporters pick a bad time to go offline.
- It's Personal: Decker takes the destruction of the crew of the Constellation very personally.
- Jerkass Has a Point: Decker argues that running to warn Starfleet from the planet killer will allow it to destroy more defenseless planets. Nobody denies this, the problem is that his insistence on attacking the planet killer will get the Enterprise destroy for nothing.
- The Juggernaut: The planet killer is indestructible. Repeated attacks by the Enterprise can't scratch it.
- Large Ham: William Windom thought the story was ridiculous and purposely overacted, not realizing he was supposed to be channeling Captain Ahab. Ironically, he wound up giving what is widely regarded as one of the greatest and most memorable performances of his career. He came to appreciate the irony of this in his later life, and he even reprised the role of Decker for Star Trek: New Voyages.
- Ludicrous Precision: Spock, as usual.Kirk: Am I correct in assuming that a fusion explosion of 97 megatons will result if a starship impulse engine is overloaded?
Spock: No, sir. 97.835 megatons.
- Made of Indestructium: The planet killer's hull is composed of neutronium, which is the super-compressed material that makes up white dwarf stars (to give an idea of how dense it is, a matchbox-sized amount of neutronium weighs six million tons). This allows it to easily shrug off everything both the Constellation and the Enterprise throw at it from the outside.
- Even the self destruct of the Constellation, which does stop the machine, only works because its more vulnerable internal systems are destroyed. The hull isn't scratched.
- Made of Iron: The Constellation is able to move, maneuver, and attack after some TLC from Scotty, even with one nacelle blown in half and holes all over its structure.
- Mechanical Abomination: The planet killer. Let's see, it's very old, its origins and motives are unknown (Kirk's speculations about it being a doomsday machine not withstanding), it's virtually indestructible, and is capable of generating a jamming field preventing the Enterprise and Constellation from calling for help. Decker notes they're not even sure whether it's a living organism or a machine. Or both.
- Mega-Maw Maneuver: Inverted. The Constellation deliberately flies into the planet killer's maw, rather than the other way around.
- Moby Schtick: One of the earliest examples in Trek, starting a recurring trend. Kirk, Khan and Picard all fall prey to the vengeance trend started by Decker. However, this particular incident was resolved when Kirk directly ordered Spock to to remove Decker from command before his reckless vindictiveness destroyed the USS Enterprise.
- My Greatest Failure: Decker sees the death of the Constellation's crew as a failure on his part, and very nearly puts the Enterprise in the same peril.
- Nice Job Breaking It, Hero!: Decker got his entire crew killed in a well-meaning but poorly thought out attempt to save their lives by beaming them to the nearest planet, that being the next one in the planet killer's path. Had he simply done nothing, most if not all of his crew would still be alive.
- Not So Different: It is inferred that before the disaster, Decker wasn't very different from Kirk.
- Off-the-Shelf FX: The show's budget wouldn't stretch to building a model of the Constellation at the same level of detail as the Enterprise (since, unlike the Enterprise, they couldn't spread the cost out by reusing it in other episodes), so the damaged Constellation was represented by a shop-bought Enterprise model with the serial number stickers applied in a different order. Averted in the remastered version, wherein the CGI of the Constellation has quite detailed battle damage.
- Oh, Crap!: Kirk, thanks to Scotty, manages to get the wrecked USS Constellation to move and fire on the planet killer before it swallows the Enterprise, unfortunately...Kirk: Mister Scott, it worked. Great.
(sees the planet killer is now turning towards his ship)
Kirk: I think it's great. Scotty, get us out of here.
- Ooh, Me Accent's Slipping: Scotty loses his brogue for a sentence when he's telling Kirk how to detonate the Constellation.
- Orchestral Bombing: Sol Kaplan's dramatic and thrilling score for this episode was so effective, it would be tracked into many later episodes of the show's second season.
- Planet Looters: The titular Doomsday Machine smashes and eats entire planets for fuel.
- Playing Sick: Inverted when Decker insists he's competent to command a starship when he is clearly mentally unbalanced. Played straight when he fakes a cough just before slugging Lt. Montgomery while being escorted to sick bay.
- Precision F-Strike: Contrary to popular belief, never once on the TV series did Bones say "Dammit, Jim, I'm a doctor, not a X!" (In this ep, for example, he says "No, I'm a doctor, not a mechanic.") Laws about swearing on TV were strictly enforced at the time. However, Decker does manage to slip in a "Hell" when comparing the machine to a devil.
- Roaring Rampage of Revenge: Decker v the planet killer.
- Reverse Polarity: What finally gets the transporter to work properly after malfunctioning for the whole episode is when Spock tells Scotty to try something called "inverse phasing". This is reversing the polarity with help from a thesaurus.
- Sacrificial Planet: The titular weapon has already annihilated a solar system and all but two planets of another by the time the Enterprise gets on the scene. It's set on a course through the most densely populated section of the galaxy to sustain itself.
- Scenery Gorn: The damaged USS Constellation.
- Scifi Writers Have No Sense Of Scale:
- In the real world, a 97-megaton explosion would be much more powerful.
- The planet killer size, as depicted relative to the Constellation, is nowhere near sufficient to contain the mass of a single planet, much less the multiple planets it does eat/would have eaten. Either it converts all that mass to energy at an astonishing rate, or leaves far more debris than we see.
- Screw the Rules, I Make Them!: Capt. Kirk finally has to use this trope by invoking his personal authority as ship's captain to get Mr. Spock to resume command of the Enterprise from Commodore Decker, who is doing his Moby Schtick. Of course, Kirk would have liked his chances facing a Board of Inquiry about this move, considering he would be arguing against a Commodore who impetuously attacked an unstoppable Juggernaut when he should have been escaping the planet killer's jamming field to alert Starfleet Command.
- Senseless Sacrifice: Subverted, actually. Decker really shouldn't have had to sacrifice himself to the machine. But the method did end up revealing a weakness they could use to destroy the machine. And really, there would have been no other more satisfying way of rounding up his emotional arc.
- Sequel Hook: The episode ends with Spock and Kirk wondering if there are any more planet-killers out there. A sequel to this episode has never been produced; Harve Bennett passed it over when looking for potential follow-up stories for the second Star Trek film in favor of "Space Seed". The popular Fan Film series Star Trek: New Voyages did a sequel of sorts to this episode (and "The City on the Edge of Forever", and "The Menagerie", among others) in their first proper episode, "In Harm's Way".
- Shout-Out: William Windom had Decker compulsively twiddle with cassette cartridges in his hand as an homage to Humphrey Bogart, who did the same thing with ball-bearings as Captain Queeg in The Caine Mutiny.
- Stating the Simple Solution: It was cut for time, but at the end, Spock notes that all Starfleet might have to do if another planet killer appears is to get an asteroid, hollow it out, stuff it full of photon torpedoes, then toss it into the planet killer's path and wait for the boom.
- Stock Footage: A shot of Scotty tossed around in engineering is recycled from "Tomorrow is Yesterday". His equipment bag disappears in this shot.
- Suicide Mission: Decker wants that machine destroyed at any cost, even his own life.
- Survivor Guilt: Poor Decker has a horrible case of this.
- Talking Down the Suicidal: Kirk re Decker. He fails.
- Tuckerization: Russ and Elliott are named after assistant directors Rusty Meek and Elliot Schick.
- Wave-Motion Gun: The planet killer's antiproton particle beam used to slice up planets for consumption and attack the starships.
- Weapon of Mass Destruction: The planet killer, hence Kirk's reference to "the Doomsday Machine" — an allusion to a popular 1960s term for thermonuclear warheads (or "the H-bomb"), as he himself points out.
- You Called Me "X"; It Must Be Serious: Spock calls Kirk, not "Captain" but "Jim" when he protests his plan to destroy the machine.