From the trailhead, you'll begin climbing immediately. The first 4+ miles are singletrack through the forest. The trail is rocky in sections and climbs constantly though not steeply, (i.e. it is quite runnable) not easy by any means but not too hard either. You'll be following the rushing stream to your left for much of this part and even have a great waterfall view.
Eventually, you'll cross a wooden bridge and soon come to an intersection with Martin Creek Trail #429
which marks the end of this section. Stay left to continue on to Foggy Dew #417 Section II