Then, why... does he believe it?

4 seconds sound clip from the The Pit and the Pendulum (1961) movie soundboard.

You can hear this line at 00:36:07 in the Blu-ray version of the movie.

Quote context

[...]

- Take this. Drink it.

- To be absolutely blunt about it, Nicholas believes that Elizabeth may have been interred prematurely.

- What?

- I hasten to assure you both that such is not the case.

- Elizabeth was quite dead. I would stake my reputation on that fact.

- Then, why... does he believe it?

- Because of what happened to his mother many years ago.

- I'm afraid I don't understand.

- I told Mr. Barnard what Nicholas saw that clay.

- No, my dear. Your mother was not tortured to death as you were told. She was tortured, yes... but not to death.

[...]