I believe that a patriotic spy, by keeping his country informed of military activity in other lands, enables his own nation to properly prepare itself...
11 seconds sound clip from the The 39 Steps (1937) classic radio play.
You can hear this line at 00:39:54 in the radio play.
Quote context
[...]
- I've noticed that the opinion held of a spy varies greatly.
- I am of course referring to patriotic spies... not mercenaries.
- How does a woman compare with a man as a spy?
- Very favorably... up to one point.
- A woman's heart will rule her head much more quickly than a man's.
- Today, there is probably one woman to every two men in the world's espionage service.
[...]