Charleston asks you to recover an Agent's mission case, and gives you a Drachnid Suit to help your endeavors while doing so.
Head to the Den of the Widow Mistress, and then stop and use the Drachnid Suit's disguise before entering.
The Suit shapechanges you into a Drachnid, thereby making all the mobs inside non-aggro to "one of their own".
Head deep into the cave to ( 426, 34, 334 ) Copy/waypoint 425.84, 33.79, 334.37 to find the Unknown Agent's Mission Case after inspecting a mass on the ground.