The time machine has been left set at the year 1930, Old Earth. As Kirk and Spock talk with the Guardians, the ancient men tell them that time moves at its normal pace all through the universe, but not here, not within the sphere of influence of the machine, for it is akin to standing on the king’s cross, a zone of no-time. Spock then says to Kirk, “You see how old they are, centuries older than any human or alien we have ever encountered? Yet they say that time moves barely at all here. Can you imagine how old they must be to have aged so much.”

The thought is staggering to Kirk, but he has barely a moment to think about it, for Beckwith manages to cleverly escape his guards, grabs a weapon and kills one of the guards as he makes a long run toward the time machine. Roused from their ruminations by the sounds of gunfire, Kirk and Spock plunge forward to stop Beckwith. He slams Spock across the jaw with the butt of the phaser rifle and keeps going, a broken-field dash that Kirk suddenly realizes is toward the time machine, Kirk takes a flying dive toward Beckwith, and manages to throw him off-balance. But Beckwith does a little dance-step of maneuvering and though he loses the phaser rifle, he hurls himself forward and in a whooooshing of space rushing to fill the vacuum where he has been Beckwith vanishes into the pillar of light, even as Kirk grabs up the phaser and fires a blast of coruscating energy at the pillar of light—now once again empty.

Beckwith has gone back. Back to the past.

Kirk dashes back to Spock. The extraterrestrial gets lumpily to his feet. He is all right. The Guardians of Forever are in a panic. They say the fact of adding Beckwith to the past has changed everything. Kirk says everything looks the same. Yes, here, on this world, everything is the same, they explain, but from here outwards everything is different. It is another universe out there.

“How? How is it changed?” Kirk demands.

They do not know. Only that the fabric of time has been warped, the river that is the time-flow has been diverted, and everything in the present has been altered. At that moment the Guardians’ city, high on one of the crags far behind them, begins to shimmer, and send out waves of light. The Guardians say they are being summoned by others, that the great ancient machines that govern the time pillar of light are registering traumas in time, and they must return to their city.

And they vanish.

Kirk realizes he and Spock and the men must get back up to the Enterprise as quickly as possible, to see what has changed there. He sends the men up first, in translation shifts that leave only himself and Spock and the two officers for the final shift.