From the Valentine dreamcatcher continue on the path that leads north as it curves around down hill towards the river. Cross the river and take the first left on the path that curves northwest under the railroad bridge. From the railroad bridge go off the trail and head straight north-northwest straight to the top of the peak. The dreamcatcher will be in a clump of there.
Finding all 20 dreamcatchers will reveal the location of the Ancient Arrowhead treasure; A unique item that makes Arthur's stamina last twice as long when using the bow.