He said, 'Someday a crazy, wild-eyed scientist, or a kid may show up asking about that book. And if that ever happens...'
9 seconds sound clip from the Back to the Future Part II movie soundboard.
You can hear this line at 00:58:44.405 in the Blu-ray version of the movie.
Quote context
[...]
- He says this book will tell me the outcome of every sporting event till the end of the century.
- All I have to do is bet on the winner, and I'll never lose.
- So I said, 'What's the catch?' He says, 'No catch. Just keep it a secret.'
- After that, he disappeared. I never saw him again.
- Oh, and he told me one more thing.
- Funny. I never thought it would be you.
- Yeah, well, Biff, you're forgetting one thing.
- You're dead, you little son of a bitch!
[...]