Approximately 100 feet beyond the East Portal Trailhead sign at the border of Rocky Mountain National park, leave the trail, descending to the left (south). Cross the Wind River then head up the steep hillside.
Continue heading to the southeast, ascending the northwest slopes of 'Thunder Peak'. Navigate past the large rock formations for 1.2 miles on the way to the summit, 1800 vertical feet above the trailhead.
From the summit of 'Thunder Peak', descend to the southwest for 0.2 miles and 500 vertical feet to the saddle between 'Thunder Peak' and 'Lightning Peak'. From the saddle, ascend the steep north slopes of 'Lightning Peak' for 0.45 miles and 900 vertical feet to the summit.
From the summit of 'Lightning Peak', descend in a north to northwest direction for 1.0 mile (losing 1900 vertical feet) to a tributary of the Wind River that originates west of Estes Cone. Stay south of the gully that descends from the saddle between 'Thunder Peak' and 'Lightning Peak'. Follow the tributary north for 0.5 miles to the Wind River Trail which leads back to the trailhead sign (now only 800 feet away), and then the remaining relatively level 1600 feet to the parking area east of the reservoir.