“Yeah,” Marty said. “I get you now.”
“Now who else did you interact with?”
“Lots of people. My grandparents, my mother and father. Biff Tannen…”
Doc Brown winced. “You looked up your parents?” he said. “How could you? That’s totally irresponsible.”
“I didn’t look them up,” Marty retorted. “I just bumped into them.”
“Tell me what happened.”
Marty recounted the events of the day. He considered them rather bland until he saw how deeply they affected Doc Brown.
“You say you saved your father from being hit by the car,” Doc said.
“Yes, but I didn’t save his life. If the car had hit him, he’d have lived.”
“How do you know that?”
“Because it’s a family joke about how Dad and Mom met for the first time when grandpa drove the car into him.”
“Good Lord! You prevented your parents from having their initial meeting?”
“Yes, but they’ll meet again. They go to the same school, you know…”
“No, no, no!” Doc Brown exclaimed. “You’ve done a terrible thing as far as your future life is concerned. Let me see that picture of your family again.”
Marty withdrew the snapshot from his wallet and handed it to Brown. His expression became grim. “Just as I thought,” he said.
“What’s the big deal?” Marty asked.
“It’s happened. This proves my theory. Look at your brother—what do you make of his head?”
He returned the picture to Marty. It was the same as he had always remembered it—except that Dave had no head. Looking closely at the photo, he saw that his brother’s head hadn’t been blotted out or torn off. Behind where his head should have been was a continuation of the rose bush which his body was blocking out. It was just as if Dave had no head when the snapshot was taken!
“Good God!” Marty whispered. “His head is gone…Like it’s been erased…”
“Erased from existence,” Doc Brown added significantly.
“I don’t understand this,” Marty said. “Or maybe I do but I don’t want to.”
Brown held up his finger. “Sssshh…” he said. “I’m developing a theory.” After thinking a moment, he snapped his finger. “Kid, we gotta get you some clothes,” he said. “You stay here and I’ll do the shopping. Tell me what your sizes are.”
An hour later, he returned from the local Sears, Roebuck with a shopping bag filled with a complete outfit. As he removed the labels from them and began to change, Marty discussed the situation with Doc Brown.
“Tell me about your theory,” he said. “Are you sure it makes sense?”
“My theories always make sense,” Brown replied. “It’s a simple genetic-mathematical extrapolation.”
“I don’t get it.”
“In plainer terms then: It was your father who was supposed to get hit by that car, not you. Thus, you interfered in your parents’ first meeting. If they don’t meet under those same circumstances, they may not fall in love. But that’s water over the dam now. We’ve got to get them to meet somehow, because if they don’t meet and fall in love, they won’t get married. If they don’t get married, they don’t have kids. That’s why your brother’s disappearing from that photograph—he’s the first since he’s the oldest. Your sister will follow, and unless you can repair the damage, you’ll be the next to fade away.”
“So what can I do?”
“Go back to school.”
“Why?”