It's not just a coincidence that the walker siblings show up at the same time as the humans. They're in the middle of the forest, and they're looking for a way to get back to the city. The narrator tells us that it's a good idea to keep the compass close by, because it'll help keep you from getting thirsty. But the narrator doesn't know how to use the compass, so he's going to have to wait until he can control himself. He's also worried that the humans are going to get too friendly with the vampires, so they'll have to hide out in the forest instead.