Start at the Denny Creek trailhead (which is now at the big parking lot for Franklin Falls off the NF-5800), up the trail to Lake Melakway, continue on up to Upper Lake Melakwa to Melakwa Pass, then descend to Chair Peak Lake and then traverse (mostly off trail, though there is a faint boot path off and on) around to the ridge below Roosevelt Peak that traverses to Gem. From Gem follow the normal trail back down to Snow Lake and then up the ridge and down to Alpental. About 12 miles TH-to-TH.
A variation is to close the loop by connecting the 2 THs on the roads. About 16.5 miles total.