Silverfish is a hiking trail around some beaver ponds in the Grater Road conservation area. Park at the Grater Road trailhead on the Amherst/Merrimack line. My brother and I put this on trails near our childhood home, hoping to bring more people to this area.
You are looking for a lock n lock not too far from a tree that has been struck by lightning.
Congrats to wemedge on the FTF!