Greg watched the Senator approach, keeping his crosshairs centered on that perfect politician smile. He couldn't wait to wipe that smile away, once and for all. This one is for South America, he thought to himself.
"Stop!" The voice came from directly behind him, but that was impossible! Greg tried to spin the laser rifle around, but his unexpected guest was too close and grabbed the barrel. No! He couldn't fail, not when everything was about to be fixed! It was at that moment that Greg noticed who he was struggling against, and relaxed his grip.
"You... you're me?"
"Yes, Greg, I'm you. I came back in time just like you did, to stop you from killing Senator Burdick. It only makes things worse." Greg lowered the rifle, frustrated and confused. How could this make things worse? The Senator had to be stopped, he just had to be. Suddenly there was a faint pop, and a woman was standing on the roof next to him.
"Greg... and Greg. I was sent back with an urgent message from your father - he says he was wrong, and you have to stop your mission." She was panting, and bleeding from what looked like knife wounds on her arm. She held up the ring Greg's father always wore, with the family crest on it, and the two Gregs exchanged glances. "Okay," one said, "But which one? We have conflicting missions."
The girl just stared. "I... don't know. I'm not even from this time, I traveled forward from a year ago to three years in the future, and then came right back to here. To be honest I have no idea at all what's going on. Um... I'm Suzy, by the way."
The door to the roof swung open, and a man ran out with a sniper rifle over his shoulder. He had clearly expected to be alone, and there was an awkward moment as everyone looked at each other and the various weapons. Finally the newcomer sighed and pointed his weapon at the floor.
"Look... I was just going to assassinate the Senator. Is that cool with you guys?" The first Greg nodded, the second shook his head, and the girl shrugged. Suzy appeared again, still out of breath, still brandishing the ring.
"Greg! I was sent back with an urgent message from your father - he says he was wrong, and you have to... oh... er, hello."
The man who had entered from the stairs smiled. "Hey sweet, you guys are time travelers too! So, listen, I'm going through time killing all of the Nobel Peace Prize winners as sort of a prank," he giggled a little in a disturbing way, "and this Senator is next on my list."
Greg just stared at him, slack-jawed. "Peace prize? He's a butcher, he kills thousands of people!" Before the man could reply to this, Suzy appeared for a third time.
"Greg! I was sent back with an urgent... oh, shit."
There was a flicker of purple in the air, and someone wearing a gold lamé jumpsuit came into being on the rapidly filling rooftop. "Greetings, from the distant future! Please listen carefully, time is of the essence. The entire universe is at risk, and -" before he could finish his sentence, a strange contraption of brass and wood crashed down on top of him from nowhere. One arm was still visible under the curled runners of the device, but it didn't seem to be moving. The occupants of the device wore absurd goggles and sported massive handlebar moustaches.
"I say, chap! The device works splendidly! Onward to the year two-thousand and twenty?" The other driver took a swig out of a flask and nodded solemnly. "Indeed, old chum. The future awaits!" and with that, they were gone - leaving only the crushed traveler and a fourth Suzy.
"Greg! I was sent back with an... oh, God, am I standing on a dead person? Did I do that?"
The first Suzy threw the heirloom ring as hard as she could, watching as it glinted briefly in the sunlight before dropping to the street below. "That bastard," she said, "he must have done something wrong when he sent me back."
Senator Burdick appeared on the rooftop as well, dressed in tattered rags. "Er..." he helpfully suggested. Simplifying things somewhat, the man with the sniper rifle shot the newly-arrived Senator and then giggled some more and vanished. The body slid to the ground, and everyone took a moment to try and absorb the situation. After a moment the silence was broken by another Suzy, which was less of a surprise each time. The door to the stairwell burst open again, and the Senator dragged a young boy onto the rooftop along with him.
"Greg, Suzy, Algernon. Wait, where's Algernon?" Everyone glanced around, sure that this comment would trigger the dramatic entry of some additional time traveler. When nothing happened, Senator Burdick continued. "Whatever. If you shoot me down there, I'll kill you Greg... at AGE TEN! Hah! You thought you could outsmart me, but... excuse me, is that me? Dead? Dressed like a homeless person?"
An older version of the man who had shot the Senator flickered and came into focus between the first Greg and the just-arrived sixth Suzy. "Hey everyone, long time no see. Anyone want to come with me to hunt cavemen? No? Suit yourselves." He disappeared into the past and mankind collapsed into a terrible, terrible silence behind him. On a grassy plain devoid of the human race, a girl appeared holding a ring. "Greg! I was sent back with an urgent message from your... father...?"