"As proof, I have copies of my letters."

"I know, Jared, I've read them," said Suzanne, his sister. "Nuclear war. Global famine. Asteroid collision. But none of those events happened."

"Of course, that's the point. I can send only small bits of matter, so I sent letters into the past to those in charge."

"How about saving our parents' lives?"

"I can't do that, Sis."

"Why not?"

"To avoid a paradox so that I can build the time portal. If I changed significant parts of my life, I might never invent it; even worse, I could never save the world."