The sentence was never finished. According to the temperature recording instruments in the bubble his body ceased radiating heat that same night.
The bubble was cleaned, fumigated, and inspected inside and out. No sign of any inimical entity or force could be found.
Silverman was Horne's replacement. When the cruiser returned six months later bringing him, Green, to be Silverman's replacement, Silverman was completely insane. He babbled about something that had been waiting outside the bubble to kill him but his nearest to a rational statement was to say once, when asked for the hundredth time what he had seen:
"Nothing—you can't really see it. But you feel it watching you and you hear it trying to get in to kill you. One time I bumped the wall and—for God's sake—take me away from it—take me back to Earth ..."
Then he had tried to hide under the captain's desk and the ship's doctor had led him away.
The bubble was minutely examined again and the cruiser employed every detector device it possessed to search surrounding space for light-years in all directions. Nothing was found.
When it was time for the new replacement to be transferred to the bubble he reported to Captain McDowell.
"Everything is ready, Green," McDowell said. "You are the next one." His shaggy gray eyebrows met in a scowl. "It would be better if they would let me select the replacement instead of them."
He flushed with a touch of resentment and said, "The Bureau found my intelligence and initiative of thought satisfactory."