They tell you what its ingredients are and how it's guaranteed to exterminate every insect in the world, but they do not tell you whether or not it's painless.
11 seconds sound clip from the Psycho (1960) movie soundboard.
You can hear this line at 01:00:43 in the Blu-ray version of the movie.
Quote context
[...]
- Mother! Oh, God, Mother! Blood! Blood!
(Vintage Ford car starts sound)
- And I say, insect or man, death should always be painless.
- I suppose, this one seems to claim more and better qualities than lots of the others.
- Sam?
[...]