From my guide:

"If you remember, in “the seed gathering run”, a horse marked your sweet fluffy wolf ass with a hoof… the next time you see Horace outside of the tavern (so only during the day), he’ll be convinced that horse is the being he was looking for, and pretty much drag you to it, but he can’t get through the barrier before the mountains (you resisting or giving in doesn’t really matter).

Go ask Jørgen (in his bar) about the horse, he is willing to give her to you, but only after the elections, which means you need to wait 3 days, then show up outside of Einar’s house or in front of the elevator in daytime to go on."

(The seed gathering run is that quest where Frode asks you to find some stuff).