This key will unlock the cell. The guard on the north wall has been bribed.

6 seconds sound clip from the The Masque of the Red Death movie soundboard.

You can hear this line at 00:42:00 in the Blu-ray version of the movie.

Quote context

[...]

- You've given away your soul.

- Yes. Gladly.

- Soon all the innocence will be gone and then I will have immortality and I shall have Prospero. But I must be certain.

- And if you were gone...

- Gladly! If there were a way.

- Would you dare to leave the safety of this castle?

- There is no safety for me here.

- This key will unlock the cell. The guard on the north wall has been bribed.

- Take your Gino and your father and go.

- But the guards... The way through to the dungeons?

- You've been to the armory and to the dungeons.

- You must make your own way. Now go. Quickly.

[...]