But underneath it all, we knew we were sitting on a barrel of dynamite and that the stoolie, whoever he was, was ready to strike again at any second.

8 seconds sound clip from the Stalag 17 movie soundboard.

You can hear this line at 00:45:28.951 in the Blu-ray version of the movie.

Quote context

[...]

- Hey! Hey, the brick Kremlin! Hey, Olga Volga, wait for me.

- Hey, Animal. The window.

- Hmm.

- So life sort of drifted back to normal in Stalag 17.

- It was a couple of days before Christmas and everything seemed quiet enough.

- But underneath it all, we knew we were sitting on a barrel of dynamite and that the stoolie, whoever he was, was ready to strike again at any second.

- At ease. At ease. At ease. All right, at ease. At ease. Mail call! All right, at ease.

- Anything for Stanislaus Kuzawa?

- First, the kommandant is sending every barracks a little Christmas present. A copy of Mein Kampf.

- All right, at ease. At ease.

[...]