The problem was self-collision. Every one of them had already been aboard during the hour they meant to enter, and the Guardian's rule did not bend: only one of a person could exist in a single moment. To set one of them down into that hour, the version already living it would have to be given up. Whoever went would be wiping themselves out of those minutes.
The relay that overloaded the helm sat in the port auxiliary junction on deck seven. For forty-one minutes that corridor stood empty, so the junction itself was no obstacle. The question was the hour, and who could be taken out of it without the hour coming apart.
"Mister Scott is holding the engines true through the time ripples for the whole of it," said Spock. "Doctor, you are in sickbay with two men on the tables. I am at the science station, running the sequence none of this works without. Remove any one of us from that hour and there is no hour to go back to."
"Then the detail," said McCoy. "Galloway. Brandt."
"They stood the perimeter, and I will not put a thing of this weight into the hands of two men whose loyalty I have never once had cause to test. One decision made alone, in the past, and there would be no recovering from it."
McCoy understood then, and did not say the rest of it.
"Lieutenant Uhura held the comm through that hour," said Spock. "There was no traffic. For forty-one minutes she had nothing in her hands and no part to play. She is the only one of us the hour can lose and still close over the gap."
Uhura had understood before he finished. "It is me."
"Yes."
* * *
She sat a long time after the others had gone. Then she took out the padd, and unlocked it, and opened a new entry.
ENTRY 651. I am going to see him tomorrow. I have wanted this for two years, and I have just been told I am going to be within ninety seconds of him and am not permitted to go and look. I want to write down, before it happens, what I intend to do. I intend to walk down that corridor and pull that relay and come home. I intend to not go up to the bridge. I am writing this because I do not entirely trust myself, and because if I am reading it afterward then it means I did the right thing.
She looked at it. Then she wrote:
If I do not come back, somebody give this to him. He will not know what it is. Give it to him anyway.