As it did every time, the crowd on the grassy knoll was milling about in the brilliant sunlight, two or three deep in spots, waiting for the motorcade to appear. From his vantage point on the overpass, Ohrbach glanced up at the window on the sixth floor of the Texas Book Depository. He thought he saw a glint from Oswald's rifle, but then Harmon nudged him in the ribs, jostling the cup of coffee Ohrbach cradled in his hands.
         "You almost made me spill this," Ohrbach said, shaking his head. "It's got honest-to-God cow's milk in it."
         "Disgusting." Harmon snuck a glance at his scanner, which the tech boys had tricked out to look like a timepiece of the era - a clunky mechanical affair which most of the people of the age appeared to wear strapped to their wrists with leather bands. "You keep staring, and Oswald will see you and get spooked. And then the time-line will be well and truly screwed. Remember he's the most important man in history. Our job is to make sure he stays that way."
         "Not a chance of him getting spooked." Ohrbach took a sip of the beverage, enjoying the rich, almost syrupy drink. "We've done this - what? Twelve times? We've never spooked him. He may be batshit crazy, but he has focus. And how the hell are we supposed to know which action is the one which makes the future end up this way or that?"
         "I'm getting some tachyon drift." Harmon shifted so his gear could project a scan that Ohrbach's augmented eyes could see. "They're on the third floor of the Depository, looks like."
         "No imagination," Ohrbach said. "Someday, somebody will materialize somewhere interesting."
         "Doubt it." Harmon moved his hand discreetly, and the images the gear was projecting shifted.
         "Can you..." Ohrbach began, but Harmon moved his hand again, and then the world faded. Then Ohrbach and Harmon were in the book depository, the light from the world outside filtering in through the big, dusty windows, illuminating the endless rows of cardboard boxes books.
         "Over here," Harmon said. "Two of them."
         Ohrbach moved around behind the stack of book crates, motioning to Harmon, who nodded, then moved around the other side of the crates toward the figures, who were silhouetted in the light of the big plate glass windows. As Ohrbach moved closer, he could see two men in yellow jumpsuits who squatted near a big, suitcase-sized box; one worked the knobs on it, while the other watched a small screen he held in his hands.
         "Excuse me, gentlemen." The two looked up, surprised, as Ohrbach unholstered his blaster and aimed it at the men. "This is a photon cannon. I have no idea what weaponry you use in your era, but you can trust me that this device is fatal. Nod if you understand."
         One of the men looked at the other, and then both nodded.
         "Good. Now raise your hands."
         The two complied, and Harmon, with surprising grace for a man of his size, walked around the two and picked up the box.
         "Says it's a Mark II transistor. Heavy as lead bricks."
         "Uh, can I speak?" one of the men - a thin, darkish man, with a neatly trimmed goatee almost identical to the one the other, much plumper man wore - asked. "It has enough lead shielding that we're safe from the radiation from the quark box."
         "You have a quark generator in that thing?" Harmon looked at the box as if it contained a rattlesnake nest.
         The men looked at each other, and then the plump one smiled. "Well, sure. How else would you make a wormhole?"
         Harmon smiled. "There are several ways. The good ones don't involve the possibility of blowing the planet into shards. Anyway, why don't we take a walk?"
         The two men looked at each other again. "Uh, we have to kill Lee Harvey Oswald," the thin one said.
         "Or, if that bothers you, we could just hit him with a stick or something," the fat one said. "I mean, if you're non-violent. We could even just sit on him until the motorcade passes."
         "You don't get it, do you?" Ohrbach shook his head. "Let's get a drink and talk about it."
         "But Oswald..." the fat one said, and then Harmon gestured with his blaster.

         The exotic dancer, a dispirited and skinny women named Coffee, rolled her hips sluggishly as the little band tootled its way through "Constantinople."
         "The Carousel Club," the thin man said. "Remember, Chan? Jack Ruby's strip club. At least you guys have a sense of humor."
         Ohrbach smiled. "A beer, then?"
         "We don't drink alcohol in our era," the thin man said. The heavy-set man - Chan, Ohrbach thought - nodded.
         "I think this is an occasion that calls for some chemical reinforcement, Jared," Ohrbach said. At least for me. One for you, Harmon?"
         Harmon nodded, then gestured to the waitress.
         "So you've guessed what's up?" Ohrbach watched as Coffee waved at the four or five people in the dingy lounge, flipped off the trumpet player, then picked up her bikini top and headed off the stage.
         Chan shrugged. "You're not going to let us prevent Kennedy from getting shot. So I'm guessing that us saving his life would screw up your time-line."
         "Yeah. If he lives, the U.S. wins in Vietnam. China goes on a nuclear building spree, and in 2042, there a war. A big one."
         "Oh." Chan looked at Jared.
         "I'm guessing this isn't good news for us." Jared looked at the amber fizzy drink that the waitress had set in front of Ohrbach. "Guess we ought to just get our stuff and go home."
         "Nope." Ohrbach shook his head. "You know, this is the part I hate."
         "We don't get to go home?" Chan finally stopped smiling.
         "Nope." Ohrbach leaned closer to the table. "See, if you don't go back, people in your era decide that travel into the past can be too dangerous, and we don't have to deal with twenty other crews from your time period. So you get to stay here. I'm afraid I already neutralized your quark generator. Someday, somebody is going to dredge the Trinity River and find the damndest collection of time-travel gear."
         "Great." Jared looked down at the greasy table top. "No robotics, no digitals, no med-techs to speak of. What's the life expectancy here? Twenty-five?"
         "Don't mope." Harmon reached for his mug. "We'll put you someplace where you won't cause trouble. We were thinking Budapest. A beautiful city, and by the time you get the language learned, you can work in the resistance to the Communists." Harmon smiled. "You might enjoy it."
         "Jared's got a family." Chan looked over at Ohrbach.
         "We're sorry." Ohrbach reached out and patted Jared's shoulder. "Look at it this way. You'll still have meaningful work to do."
         Jared looked like he was going to cry.
         Chan shook his head. "You know, I think I will have a beer."

         Then, Ohrbach and Harmon were back on the overpass looking over the grassy knoll, the sun gleaming off the last police cars as they swept the streets clear of pedestrians.
         "Have you ever thought about what happens to us when nobody else tries to come back and change the past?"
         Harmon looked at Ohrbach, frowning, then back at the heavy body of his watch. "We go back to a civilized era. And that's that."
         "Maybe." Ohrbach looked across at the Texas Book Depository. "None of the guys from the eras before ours have gone back. We haven't let them."
         "So?" Harmon pulled a screen up into the air before the two. "We're the most advanced era that has come back."
         "So they told us."
         "Hey. Getting some drift over here."
         On the ghostly display screen floating in front of the two, there was a slow rise, then a giant spike in the tachyon levels.
         "Another group," Harmon said. "Very high tachyon pulse. Some really amazing tech here."
         "And a new location. This one's different. Should we..." Ohrbach started, but then the things in his vision wavered, and the two were standing in the grim alley at the back of the Depository, looking at the sooty back of the building where, on a loading dock, two very thin men stood in tight-fitting silver garments.
         "Brethren," one of the men said.
         "Damn, you guys look strange," Harmon said. "Anyhow, our job is to keep you from killing Oswald."
         As Ohrbach watched, the two men looked at each other. The two were exceedingly thin, and neither had any hair, or eyebrows - or, as Ohrbach watched as one lifted a skeletal hand and waved it, fingernails, either.
         "Hey. What did you do with our gear?" Ohrbach reached for his blaster, which was gone as well.
         "We should like to inform you of our origins and purposes," one said, the voice seemingly coming from nowhere, and Ohrbach realized that the tiny mouth that the men had was not sufficient to speak. "We have come here from well beyond your own time; as you have noted, it has been a sufficient span of time that we are markedly different in conformation than are you. You may infer from that the vast span of time that separates us."
         "Gotcha," Harmon said. "And your technology is really something."
         "We are incapable of killing; it has been bred from us as surely as has our ability to speak audibly," the second man said; Ohrbach thought he was indistinguishable from the first, except that some sort of subtle cue made Ohrbach realized that he - she - was a woman. "Thus we must ask you to perform this disagreeable task for us."
         "You want us to kill Oswald?" Ohrbach said. "We've devoted years to keeping that little bastard alive."
         The two beings looked at one another, then at Ohrbach, clicking their tongues.
         "I think they're laughing at you," Harmon said.
         "Maybe." Ohrbach looked at the two thin beings, their skin a milky white, bluish veins showing on their foreheads and arms.
         "That is not what we want at all," the female being said. "It is he -" she pointed with a bony finger at Harmon - "who must die."

         Then there was a flash, and the group was nowhere in particular, in a place where there was only a sort of dull gray illumination from nowhere, like being in a gigantic frosted plastic sphere with illumination coming from outside.
         "There is no time here," the woman said. "No place. Here we can talk."
         Ohrbach looked at Harmon, who was frozen standing in the position in which he had been standing outside the Book Depository.
         "He is not in time at all," the woman said, and the man moved his head quickly to the left.
         "That means agreement? That head movement?"
         "Affirmative," the woman said, and both moved their heads to the left. "Now. You and he never return to the future. Your technology does not permit it. From his behavior in the future, we gather that neither of you understood that you could not return."
         Ohrbach looked at Harmon, who was still frozen, eyes wide. "We were told we would go back when groups stopped coming to stop the assassination."
         "Understood. What in fact happens is that you remain here, and become a repairman for water systems."
         "A plumber." Ohrbach shook his head. "Not exactly what I'd planned."
         "Understood. You prosper. But he - " again, the woman raised a bony finger toward Harmon - "he does not prosper. He has a child, who is the Angel." And both she and the man bowed their heads, folding their hands in front of them.
         "What the hell does that mean?"
         The woman raised her head. "His daughter is the salvator mundi. The savior of the world. The Angel." The woman's telepathic voice communicated such a feeling of holiness, of sanctity, that Ohrbach felt the hair on his arms prickle. "But this man is cruel to the Angel." She bowed her head again, then raised it. "We imagine that Mister Harmon misses his true time, and feels out of place. He punishes his daughter. She learns from his cruelty the art of happiness, of peace. And she communicates it to the world."
         "Um. Then why don't I know anything about it?"
         The two clucked their tongues. "You are long since dead when she writes her book. She, in point of fact, is long since dead when the world comes to know her as a deity."
         "So she's your god."
         The two clucked their tongues again. "Yes," the man said. "But more than that. We have the intellectual tools she gave us. They eliminate bad thoughts, permanently. There is no suffering in our time. No misery, no violence. And that is why he must die. She frees us of war, and hence of weapons. Thus we are defenseless when we face our greatest challenge. Thus she must never live. We could not kill her, of course. Not even by proxy. But we, or rather you, can kill her father."

         The aliens called themselves the Freith, or at least that was as close as the devices which served for vocal communication could manage to get to the sounds the aliens made. Attempts on the part of humans to negotiate, Ohrbach learned, had been ignored as the aliens had moved from human settlement to settlement, from planet to planet, destroying.
         And the humans, peaceful, harmonious, and happy, could not respond in kind. The outcome was that the humans were slaughtered wherever and whenever the aliens encountered them.
         The two told, or, better, showed Ohrbach how the few remaining humans cowered on Earth in brilliantly constructed bunkers, searching the most ancient archives of the race, until they learned what had happened before the Angel, the woman who started the history they knew. They resurrected the technologies of time travel. And they learned - to their horror - that humans had not always been pacific, that misery, not happiness, had been the standard lot of humans, that one woman whom they had thought a mythic goddess was really, truly human - the architect of all the millennia of bliss that followed.
         And they decided that survival was more important than happiness, and used their last resources to send the two humans - the two last humans, perhaps - back in time to change everything.
         To reintroduce suffering and war in order to save the race.