Stardate: Not available (although the Constellation engaged the machine at 4202.1)
Original airdate: 10/20/1967
Writer: Norman Spinrad
Director: Marc Daniels

Guest stars:

William Windom    Commodore Matt Decker, commander of the USS Constellation, died while attempting to destroy the machine

Elizabeth Rogers        Lt. Palmer, communications officer in place of Uhura

John Copage             Elliot (unknown, see damage control party list)
Richard Comton          Washburn, member of the damage control boarding party
John Winston            Kyle, transporter chief
Tim Burns               Russ (unknown, see damage control party list)

Crew Appearances:
Damage Control Boarding Party to the USS Constellation
Kirk, Scotty, McCoy, Washburn, and two unnamed gold shirts.

Spock- left in command of the Enterprise
Sulu
Unnamed navigator
Mr. Montgomery, security guard beat up by Decker
Science officer Misada- former of the USS Constellation, dead on the third planet.

Story:

After several star systems have been destroyed, the Enterprise investigates the situation and discovers what's left of the USS. Constellation, same class star ship as the Enterprise, with her commander, Commodore Matt Decker, the only person found on board. He relates a terrifying tale, detailing how a tunnel in space emitted energy waves that sliced up whole planets which it devoured. He beamed his crew down to the third planet in the hopes of protecting them, but that particular planet was the next target. Kirk and Spock come to the conclusion that this thing is actually a doomsday machine - an ultimate weapon - created by a long dead race, that has been destroying planets for centuries. Now the hope is that the Enterprise and whatever can be salvaged of the Constellation will be able to defeat it before it continues on its way.

The doomsday machine, a robot weapon made of pure neutronium that uses a force beam of pure anti-proton to chop up planets and use them to refuel, becoming completely self sustaining and indestructible, origin unknown.

System L 373 a 7 planet system reduced to rubble by the machine
System L 374 a system with only the inner 2 planets left after being attacked by the machine where the Enterprise finds the USS Constellation, disabled and crewless.

Rigel Colony (Rigel System)-a populated system, new destination of the doomsday machine after eating up the L 373 and 374 systems

Quotes:
"They say there's no Devil, Jim, but there is; right out of hell, I saw it."
_______________________
"Matt, where's your crew?" Kirk
"On the third planet." Decker.
"There is no third planet." Kirk.
"Dont you think I know that? There was, but not anymore." Decker. (one of the most moving scenes in star trek. Great Actor!
________________________
"I'm a doctor, not a mechanic." McCoy.
________________________
"you mean you're the lunatic that almost destroyed by ship?"
________________________
"Vulcan's never bluff." Spock.