Go to the murder site and the gazebo.
Be sure you also have the UV lamp and wet wipes.
Clean the info stand pass the gazebo that has words covered with the wet wipes. Get a clue then.
From this info stand, go forward and see the cavelike rest area where you can sit and rest at right side of path.
From here - go forward and look for the wooden birdhouse up a tree at left side.
Look close and use the UV lamp on the wood of the birdhouse.