Yes, but if there are Martians...?
4 seconds sound clip from the X Minus 1 - Mars is Heaven by Ray Bradbury classic radio dramaseries.
You can hear this line at 00:23:24 in the radio play.
Quote context
[...]
- But there was no Anna, I'd been nursed by a man.
- Why? A whole crew was thinking of home.
- Suppose the Martians read our minds.
- Yes, but if there are Martians...?
- I left my pistol downstairs.
- Do you think there's something to this?
- It's a perfect trap, Captain.
[...]