- Oh, Dorothy's mother? does she have to be up to something?
- She usually is.

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

You can hear this line at 00:11:39 in the radio play.

Quote context

[...]

- Say, you're worrying an awful lot about this business. Forget it!

- I'll open it... I'm Mrs. Charles. Come in, Mr. Macaulay.

- Hello Macaulay!

- Hello Charles, how are you?

- Fine! Sit down.

- Thanks.

- Eh, Dorothy told me you here. I took the liberty of coming to see you.

- Of course.

- Eh, Charles, what's Mimi up to?

- Oh, Dorothy's mother? does she have to be up to something?

- She usually is.

- Trying one way or another to get money out of Wynant.

- I wanted to find out if you were... sleuthing for her.

- I haven't been a detective for four years.

- You don't say.

- My wife's father died and left her a lumber mill and a narrow gauge railroad and a couple of other things. And I'm looking after them.

- I see. I see.

[...]