 What central theme of the story is revealed in the conclusion?
A gun is an interesting weapon; it can be hired, of course, and naturally doesn't care who hires it. Something much the same can be said of the gunman, too.... The pleasurable, comfortable, warm feeling began spreading over him, the way it always did. The evening was dark, it was unlikely that the other even saw the circle of steel that was the mouth of the shotgun barrel, now resting on the car's window ledge. And at that moment, the universe caved inward upon Joseph Marie Prantera. There was a falling through all space and through all time. And he came out of it as quickly and completely as he'd gone in. A door slid open in the wall in a way that Joe had never seen a door operate before. The other spoke precisely and slowly, the way a highly educated man speaks a language which he reads and writes fluently but has little occasion to practice vocally. With the exception of a faint nausea, which brought back memories of that extreme condition he'd suffered during ... during what? It opened on his approach, the door sliding back into the wall in much the same manner as the room's door had opened for Reston-Farrell. He looked out, however, not on the lawns and walks of a sanitarium but upon a wide boulevard of what was obviously a populous city. Reston-Farrell had approached the door by which he had entered and it reopened for him. Two were seated there now, papers, books and soiled coffee cups before them. Reston-Farrell, the one Joe had already met, was tall and drawn of face and with a chainsmoker's nervousness. He wondered, all over again, if this was some kind of pressure cooker. The maternal linage was almost universally ignored." Whatever the something else was, a slot opened in the middle of the table and a glass, so clear of texture as to be all but invisible, was elevated. "To Nuevo Los Angeles and to the year—" Brett-James looked at his companion. "What is the date, Old Calendar?" "2133," Reston-Farrell said. Briefly, we have transported you, I suppose one might say, from your own era to ours." Reston-Farrell said, "Suffice to say, you are now one hundred and seventy-three years after the last memory you have." Reston-Farrell said, "Mr. Prantera, we have brought you from your era to perform a task for us."
 If someone is willing to take a life, you cannot trust them to make moral decisions
 The more good you do for others, the more opportunity for them to criticize you  If someone is willing to take a life, you cannot trust them to make moral decisions  When cornered, threatened creatures will do anything to survive  The prosperity of a nation is more important than any individual life