He knows it was somebody else on the train and he's dug up a witness he thinks can prove it.

5 seconds sound clip from the Double Indemnity movie soundboard.

You can hear this line at 01:24:46 in the DVD version of the movie.

Quote context

[...]

- What's the matter?

- Everything's the matter.

- Keyes is rejecting your claim.

- He's sitting back with his mouth watering, waiting for you to sue. He wants you to sue, but you're not going to.

- What's he got to stop me?

- He's got plenty.

- He's figured out how it was worked.

- He knows it was somebody else on the train and he's dug up a witness he thinks can prove it.

- Prove it how? If he rejects that claim, I have to sue.

- Yeah? And then you're in court and a lot of other things are going to come up. Like, for instance, about you and the first Mrs. Dietrichson.

- What about me and the first Mrs. Dietrichson?

- The way she died.

[...]