But that's not the truth.

2 seconds sound clip from the Back to the Future Part III movie soundboard.

You can hear this line at 01:14:26.220 in the DVD version of the movie.

Quote context

[...]

- Please, Emmett. Please, I have to know. If you sincerely do love me, then tell me the truth.

- All right then. I'm from the future. I came here in a time machine that I invented, and tomorrow I have to go back to the year 1985.

- Yes, Emmett. I do understand. I understand that because you know I'm partial to the writings of Jules Verne, you concocted those mendacities in order to take advantage of me.

- Oh! I've heard some whoppers in my day, but the fact that you'd expect me to entertain a notion like that is so insulting and degrading!

- All you had to say is, I don't love you, and I don't want to see you anymore. That, at least, would have been respectful!

- But that's not the truth.

- Emmett. What can I get you? The usual?

- No, Chester, I'm gonna need something a lot stronger than that tonight.

- Sarsaparilla.

- Whiskey, Chester.

- Whiskey? Emmett, are you sure? You know what happened to you on the Fourth of July.

- Whiskey.

- Okay, I ain't your papa. Just don't want to see you do the wrong thing.

- And you can leave the bottle.

[...]