The secret of invisibility lies there in my books.

3 seconds sound clip from the The Invisible Man (1933) movie soundboard.

You can hear this line at 00:48:43.721 in the Blu-ray version of the movie.

Quote context

[...]

- I want to help you.

- Why did you do this?

- For you, Flora. For me?

- Yes, for you, my darling.

- I wanted to do something tremendous, to achieve what men of science have dreamt of since the world began, to gain wealth and fame and honor. To write my name above the greatest scientists of all time.

- I was so pitifully poor. I had nothing to offer you. I was just a poor, struggling chemist.

- I shall come back to you, Flora, very soon now.

- The secret of invisibility lies there in my books.

- I shall work in Kemp's laboratory till I find a way back. There is a way back, Flora. And then I shall come to you.

- I shall offer my secret to the world, with all its terrible power.

- The nations of the world will bid for it. Thousands, millions.

- The nation that wins my secret can sweep the world with invisible armies.

[...]