Gunmar is just outside the Broken Limb Camp. After you persuade her, or bring her a Dwarven Gyro, she says she will meet you at Fort Dawnguard. I have a feeling it doesn’t take much to persuade her because I did not have a very strong speech level. I was able to persuade her to forget that nonsense and to move on and the fort.
Heck you might just have one on you from your travels or find one in a shop that you have sold to in the past. You can find these at any of the dwarven mines. After convincing her there is a problem with vampires she needs one Dwarven Gyro before she leaves. She will talk about how her and Isran had a falling out. You will meet Sorine Jurard in a nice spot by two waterfalls. After I got to Dragon Bridge it was a pretty rocky slope but easy enough to navigate through, especially on a horse. Either way fast travel to the closest point that you can to the quest marker on the map and start hoofin’ it. Unfortunately for me, and for the guide I will be starting at Haafingar Stormcloak Camp. If you have the fast travel point for Karthwasten that is a good place to start.
