Getting There: At the top of Thompson Pass trail #404 takes off just on the Montana side of the pass. There is a sign there where the trail takes off from the parking lot. The trail starts out very flat as you walk on the remnants of an old road and along the old canal. The canal used to bring water over from Montana to the mining activities on the Idaho side of the crest. It is about a mile of good walking and then you turn up the hill into a series of switchbacks. 
After a bit the trail lines out at a good grade for about 1.5 miles before you top out and drop down a grade for a bit before going uphill again; but not nearly at the same grade. There isn’t any water along the entire route until just before the Lower Blossum Lake, so bring enough water for yourself and your dog. Except for at the 4 lakes there just isn’t much water available along the loop.
To reach the Upper Blossum Lake cross over the outlet and head along the lower lake on a good trail; still trail #404. The upper lake is about a mile of easy walking in the shade, stay to the right on trail #537 at the half mile mark where the left fork (trail #404) continues to Pear Lake and eventually the state line trail.
After visiting Upper Blossum Lake return on trail #537 and hang a right on trail #404 to Pear Lake. Trail #404 does climb a good bit with a couple switchbacks as you pass over the ridge from the Blossum Lake drainage into the upper portion of the Glidden Gulch but is still a pleasant hike. The trail eventually heads downhill to the lake.
Pear Lake is a good place for a longer rest and possibly lunch. Continue past Pear Lake on trail #404 and climb up to the state line trail, which is just a continuation of trail #404. Head Northwest (right) and up on the trail for about 1 mile until you look directly down at Upper Blossom Lake from the ridge at a steep and rocky switchback. 
The trail will swing southwest off the ridge and into the trees just after that. If wanting to climb Granite Peak, stay on the trail. It will connect with the rocky road from the Burke side in less than a mile.
Leave the trail at that point and follow the ridgeline north. Stay on the ridge until just before the dividing ridge between Revett and Blossum Lakes; there is a bit of a saddle there.
At that point drop down the east side of the mountain, swinging below the rocky area and heading to the low saddle. Aim to split the prominent rockslides on the east hillside to attain the low saddle along the dividing ridge; see the cross-country image. Head straight down through the rockslide on the Revett Lake side, then angle down towards Revett Lake taking the best route available. This portion is not steep and surprisingly not very brushy. You should end up at the west end of Revett Lake where you will pick up the shoreline trail around the lake. From there it is an easy hike back to the Revett Lake trailhead and back to Thompson Pass on the road.
The day Colter and I completed this loop there was a gentleman that hiked the same route except he went on to Granite Peak and then dropped into Revett from there. We also saw a man and his teenage son climb (with full backpacks) over the ridge from Lower Blossum Lake and drop into Revett Lake via another low saddle, we saw them at Revett Lake while we were having a snack.
I am including some pictures from Granite Peak that I climbed up in 2020.
