A False Front

Information
This quest belongs to The Imperial Legion quest line.

Quick Walkthrough

 * 1) Report to Rikke in the Pale Imperial Camp and go to one of the inns as ordered.
 * 2) Make the inn keeper of one of the inns tell you where the courier is.
 * 3) Find the courier, kill him and take the "Stormcloak Documents".
 * 4) Give the documents to Rikke and, after she's done altering them, take them to the Stormcloak commander in Dawnstar.
 * 5) Report back to Rikke.

Detailed Walkthrough
Report to Rikke in the Pale Imperial Camp and she will tell you to hunt down a Stormcloak courier so that she can alter the carried documents, giving the Stormcloak commanders false information. You are supposed to go to either the Nightgate inn (southeast of Dawnstar), or the Candlehearth Hall in Windhelm.

When you get to either one of the inns, talk to the inn keeper. To get the information you want, you can bribe, intimidate or persuade him. He will tell you the courier just left. You can wait for him at the inn, as he will return after a couple of hours, or you can follow your quest marker showing where the courier is going.

When you find him, kill him and take the "Stormcloak Documents" he is holding. Bring the documents to Rikke and she will "correct" them, and then order you to take them to the Stormcloak commander in Dawnstar. Give them to the commander and then head back to Rikke.