"What are these kids doing so late?" thought Arthur, looking at them from the top of the tree.
He heard the brief conversation between the two kids, with one speaking about hearing screams, and the first thing that came to his mind was Jake and Agatha.
So Arthur followed these two kids during the night, and no one noticed a thing. So if powerful mages could not feel his presence, how would two kids?
They moved outside the tribe, inside the nearby forest where the elves usually hunt or the kids used it to play hide-and-seek. The kids moved like they knew the forest well, but it was still easy for Arthur to follow them, considering their slow movements and his keen senses.
The kids stopped in front of a specific tree, and one of them said, "this is the place. I heard screams coming from this tree! I know it sounds crazy, but I am telling you the truth."
Now that the two kids were there, the screams had stopped, making it look like the other kid was making things up.