Automated destroyers! Minutes to save a dying planet!


Invasion of the City Builders, Part IEdit

Captain's log, stardate 20:14.6. Mission has been delayed by direct meteorite hit on rocket engine number four. Repairs being made. Expect to continue toward objective shortly...

An engineering crew completes repairs and the USS Enterprise resumes its course to planet Alpha Z-21, also known as "Planet Questionmark."

To prepare for the research mission, Lieutenant Commander Spock and Captain James T. Kirk review the planet's history using radio film footage taken by a "deep galaxy ship" before it exploded. The brief footage shows a high level of civilization with advanced technical machinery featured prominently.

Upon arrival to the mystery planet, Spock notes a high-oxygen reading with indications of water also present. The Enterprise goes low into the planet's atmosphere where observations note that much of the planet is a massive, empty city bearing no signs of catastrophe. Kirk orders the ship into orbit and an exploration team transports to the surface.

As Kirk, Spock, and the rest of the team beam down, their presence is noticed by members of the indigenous population. Before anyone can do anything, a convoy of heavy equipment approaches, causing the ground to shake. The equipment contain no operators but begin creating buildings and roads rapidly to extend the existing city. Some of the planet's population attempt to board one piece of machinery only to be thrown off. Kirk stops the machine using a laser rifle and the heavy equipment withdraws from the scene.

Using the language Esperanta, Kirk communicates with the aliens, who thank him. The leader, Krill, explains he's the leader of all who remain of the planet Zarta. 150 years ago, his people were a flourishing race of many millions. Their civilization experimented with using machines to replace manual labor with the machines becoming more and more sophisticated. The nadir of this technological progress was the city builder, a complex machine designed to build cities with great technical precision. However, the city builder began to construct buildings and other facilities on its own. Construction soon got out of control, threatening the planet's populace. Because machines had been responsible for the planet's technological progress for so long, the populace did not understand the complexity of the machines currently existing and eventually lost their technological knowledge prior to the rise of the machines.

Part II: The Bridge to CatastropheEdit

After Krill describes their planet's history, three city builders threaten the 10,000 acres of open land left on the planet. Kirk suggests using earth disintegrators to make a trench in hopes of halting the thousand-ton machines. One of the giant gadgets falls into the trench but begins building a structure to pull itself out. Kirk then orders a force field erected but that eventually proves fruitless as well. When the city builders reach the river, they begin constructing a bridge to cross the obstacle.

Exasperated, Spock puts forth that a weakness might be found in the alien metal making up the city builders. Kirk orders a metallic test kit transported down but Krill skeptically notes that it may take years to discover a weakness. After boarding a river boat, the captain prepares to fires his laser rifle at a hoisting girder but the boat is rammed by Krill, who has become jealous of Kirk's leadership during the crisis. Spock subdues Krill long enough for Kirk to succeed in his plan.

Spock's analysis reveals a molecular flaw in which the alien metal breaks down when exposed to an ammonia (NH2) solution. Once chemicals and vats are transported to the surface, Kirk sets out to stop the city builders but Spock stops him, saying Krill should lead his people. Krill rejects the leadership role in favor of going alone.

As Krill sprays the ammonia solution at a bridge support, a city builder drops hot rivets into his boat. To protect himself, Krill takes the boat under the bridge and resumes his work and is successful. Kirk has the Enterprise find the rest of the city builders and then joins Krill in destroying them.

Krill thanks Captain Kirk for his help before going on to destroy the machine-building factories. He notes that destroying the useless cities to reclaim the land will take generations. After the exploration team beams back to the ship, the Enterprise leaves orbit.



KazarJames T. KirkKrillSpockUrgo familyZika
Referenced only 
Leonard McCoyJanice RandNyota Uhura

Starships and vehiclesEdit

USS Enterprise (Constitution-class)
Referenced only 
deep galaxy ship



Races and culturesEdit

HumanVulcanZarta native

States and organizationsEdit

Starfleet Command


ammoniacity builderEarth disintegratorEsperantaforce fieldgalaxy minutelaser riflelunar hourmagno-hookmeteoritemoon monthoxygenradio filmstock marketTest Z-12water



  • The picture in the lower left hand part of the cover is part of a still from "Charlie X." McCoy, Uhura, and Rand do not appear in this issue at all.
  • The stardate in the captain's log has a colon after the first two digits.
  • The radio film reviewed is stored on an object resembling a 16mm film reel.
  • Kirk uses a microphone to communicate with the bridge (called "control" in this story).
  • Many times in the story, the Enterprise is depicted with flame exhaust emanating from her warp nacelles.
  • The uniforms and transporter room depicted are unlike anything featured in the television series.
  • The landing party (called "exploration team" in this story) have backpacks and utility belts as part of their standard gear.
  • Kirk's use of a laser rifle is odd, considering he used a phaser rifle in "Where No Man Has Gone Before."
  • A solution containing NH2 (ammonia) is described as an "amino acid" solution, which is incorrect. A solution containing ammonia is an amido acid.



published order
Previous comic:
#2: The Devil's Isle of Space
TOS comics
(Gold Key)
Next comic:
#4: The Peril of Planet Quick Change
chronological order
Previous Adventure:
The Final Truth
Memory Beta Chronology Next Adventure:
Ice Journey

External linksEdit