With lights flashing and counters spinning, John unlocked the secrets of time. Having dreamed of time travel since adolescence, he sent himself back thirty years. A 16 year-old him stared back at him. He began to talk, but the younger-John stopped him. "Please. You know I've been expecting this for years now." Younger-John opened a drawer and pulled out a knife. "What the hell are you doing?" asked John.
"People always ask what would happen if you went back in time and killed your own grandfather. But cutting off the past is so simple, so obvious. The real question is what happens when we cut off our own future."
"But... this is wrong! I don't remember any of this!"
"Couldn't you guess? You never remembered this as a kid at all. What did you expect?" Younger-John pulled out a small bottle of pills from his pocket. "These'll knock my memory back a couple of hours. Depending on what happens..."
With knife in hand, shaking with youthful nervousness, scientific excitement sparkling in his eyes, the past advanced on the future.