Roy's first encounter with the boy he knows as Mullet Fingers wasn't a very pleasant experience; then he was tied up. As Roy comes looking for Mullet Fingers again, he's mentally prepared himself for a similar experience. In fact, he's actually prepared a little speech for the occasion that he hopes will persuade this strange kid that Roy is someone to be trusted, someone who can help him.
But Roy doesn't get a chance to make his speech. Because when he arrives at Mullet Fingers's makeshift campsite, there's no sign of the boy anywhere. He's vanished without a trace.
It seems that Mullet Fingers has taken off all of a sudden because he doesn't feel comfortable about spending too much time in one place, especially now that Roy knows about the whereabouts of his campsite.
This is because Mullet Fingers is on the run from a special school, from which he escaped after just two days. Not unreasonably, he doesn't want to return to school, and so he figures that the best way of evading capture is by moving round from place to place. Roy may genuinely want to help Mullet Fingers, but Mullet Fingers doesn't know that, so he remains focused on not getting caught and sent back to school.