- Why not?
- I want to lie low till I get the whole dope. I don't want to go off half-cocked.

6 seconds sound clip from the The Thin Man (1936) classic radio play.

You can hear this line at 00:44:33 in the radio play.

Quote context

[...]

- The clothes for instance. They were carefully preserved, and the body was just as carefully destroyed.

- The person who killed him counted on one thing: that all skeletons look alike.

- Well, don't they?

- Sure.

- I remembered that Wynant had some shrapnel in his shin. They found it under the fluoroscope.

- How long has he been dead?

- Couple of months anyway.

- Then he couldn't have committed those other murders.

- Smart gal.

- Wynant dead? Does Dorothy know?

- No. Nobody but you. I didn't even tell Guild.

- Why not?

- I want to lie low till I get the whole dope. I don't want to go off half-cocked.

- What are you going to do?

- I'm going to get the real murderer.

- I've got an idea. Want to see me take him?

- Yes!

- Got a nice evening dress?

- I've got a lulu. Why?

- I'm going to give a party, everything from Russian caviar to Camembert cheese, an orchestra behind the palms, and I'm going to invite all the suspects.

[...]