Synopsis:

Following a trail of smashed planets the Enterprise comes upon the badly damaged Constellation and her only remaining crewmember, the Captain, Commodore Decker.    He tells them about a machine that destroys planets and uses the raw materials for power.   After the Constellation had been damaged Decker sent his crew down to a planet which was subsequently destroyed by the planet killer.     While Kirk and a landing party try to prepare the Constellation for towing the planet killer returns.

This episode has some of the best special effects that the Original Series used.   There are a lot of battle scenes (for TOS) and the drama and suspence are as high as it gets.   This episode definately has some parallels for the sixties and our times now.   It asks the question, "If a weapon is so destructive that it kills both sides, is it a weapon or a mistake".   I think it does a fine job of bringing this to light at the end.