You get this quest after completing The Defias Brotherhood I, by speaking to Wiley the Black in the Lakeshire Inn. He says:

What I am about to tell you could cost me my life.  The Defias gang is up to something big.  Last I heard they were working in conjunction with various gnolls, kobolds and even goblins.

Take this note to Stoutmantle.  It explains as much as I know on the subject.

Travel to Westfall
Speak to Gryan Stoutmantle

Now it?s back on the gryphon to Westfall, where Gryan Stoutmantle is waiting in front of the tower. Speak to him and he says:

Good to see you back. What did Wiley have to say for himself?

Bah! I should have let that scoundrel rot when I had the chance. But his information is crucial. Good work.

So, you thought the running was over now? Not yet?Gryan has another little errand for you to run, this time in The Defias Brotherhood III.