They strike out toward the source of radiation and in the far distance see a series of great mountain peaks, rising up like shards of glass from an ocean of silver. They get a distant impression of a great city on the furthest of those peaks, a series of spires that tower into the cadaverous gray sky without warmth or welcome.

But they go toward the spires and soon they find themselves on a mountain top near the city. As they top a rise, they are astounded to see a group of men…but such men as the explorers from Earth have never known:

Old they are. Old as the chill and dying sun that casts only shadows on this empty planet. Old as thought, old as time, old as the cinder on which they live. Nine feet tall, and shapeless beneath the long white robes that reach to the mist-laden ground. Even taller if one allows their mitered headpieces. Taller still by the lengths of their snow-beards, the only part of them other than their lined and weary faces that shows from their clothing.

Kirk and Spock register astonishment at finding these ancient creatures, but the old men finally speak, after long beats in which their motionlessness makes us suspect they may be stone. And this is what they say:

We are the Guardians of Forever. We have been here since before your sun burned hot in space, before your race came into being. We have been here when this area of space was so filled with young suns that it was always high noon from their light.

“But why do you stay here when this world is cold and empty?” Mr. Spock demands.

Only on this planet do the myriad pulse-flows of time and space merge. Only here do the flux lines of Forever meet. Only here on this empty corpse of a world is there a gateway to the past, where the time machine created by the Ancients can work. Only here. And we were set to watch the time machine, so many hundreds of centuries ago that even we do not have clear memories of it.