At the end of In the Woods, Rob goes back, er, in the woods one last time. The woods are about to be bulldozed for the highway, and Rob chats up one of the construction workers.
The worker has found something the archeologists missed: an arrowhead. It "was cool in [Rob's] palm, heavier than you might expect. Narrow grooves, half worn away, formed a pattern on one side. […] No more than a stick figure, with the wide, pronged antlers of a stag" (25.143). What the heck could that be? Evidence of human sacrifice? A supernatural force in the woods? Whatever it is, it's no lucky charm. Or probably not in Rob's hands, anyway.
We'll never know. Rob gives it back to the worker to give to his grandson. This gesture shows us that, whatever caused the disappearance of Peter and Jamie in 1984, Rob is finally going to try to put it behind him. He needs to visit the woods to say goodbye, but he doesn't need a token from them to carry forward. However, the arrowhead leaves "slender red marks" (25.149) across Rob's palm, symbolizing that the scars of the past will always stick with him.