Damon collapsed at the center of the road after his battle with the vampire and needed the help of the city guards to return to the Ross family castle. He spent the entire night and the next day unconscious, while Lord Ross got their own side of the story of what happened.
Damon's wounds weren't healing and he had a bad fever. He only regained consciousness in the evening of the next day, only to see Lord Ross and other members of the Ross family in the room.
The old physician went through Damon's condition and shook his head. He could tell Damon was reacting to some sort of venom, but he had no means of dealing with it.
Supernatural things cannot be handled through physical means and in a small city like this, it was nearly impossible to find a good healer. If the Ross family wanted to help alleviate Damon's condition and hasten his recovery, they would need to hire a proper healer from the church.
