This is an off-trail route. Only come here if your navigation is up to the task of finding your way where there are no trails to follow, and practice Leave No Trace to avoid damaging fragile terrain.

This has got to be the most varied hike on Rainier:

• Start up an old, unmaintained trail from the ranger cabin at Mowich Lake (facing from the lake toward the front steps of the cabin, it's to your left, and to the left of the path that accesses the ranger outhouse). It's steep, rooty, and rough: a good way to get most of the elevation gain of this hike out of the way early.
• Enjoy as the terrain opens from forest into a world of meadows, streams and small waterfalls. It feels like an older cousin of Spray Park that grew up on the wrong side of the tracks: you can tell they are related, but this one hasn't shaved for a few days and you wouldn't want to get on the wrong side of them.
• Arrive at Knapsack Pass, which is a true take-your-breath-away moment. If you started early in the morning like me, you'll have been climbing in shadow this whole time, and without Rainier views. All of a sudden there's sun on your face and a volcano right in front of you!
• The descent to the east of Knapsack Pass is an adventure. It's steep, and consists of loose scree where the path may not be obvious. When I visited the bottom 30 feet of this slope was still covered in snow, but it had a nice safe runout, perfect for a glissade.
• Turning south you'll traverse below East Fay Peak, which is the source of a large talus field. Snowfields linger here through most of the year, so you may be clambering over boulders, hiking over snow, or both.
• After skirting around the east flank of Mount Pleasant you'll enter upper Spray Park, which is a wonderland of wildflower meadows, summit views, meltwater ponds, and views to the north over Mist Park.
• The Knapsack Pass trail ends upon joining the Spray Park trail. Turn right here and enjoy the glories of Spray Park on the way back to your car: some of the finest wildflower meadows on this planet followed by a descent into lush forest and the spectacular Spray Falls, on trail that's no longer unmaintained or lacking crowds of other hikers :-)

This is a hike, not a scramble, but it's on the scramblier end of things that count as hikes. Route-finding is challenging in places. There are no signposts identifying the several climber's trails that turn off toward Fay Peak, First Mother Mountain, Mount Pleasant, etc. The scree, talus, and snowfield sections may have no visible path to follow: I found no footprints ahead of me on the snow. Only come here if your navigation is solid.

Being a loop, of course you could also hike this counterclockwise, but that would be foolish. It's easier to get the steep parts out of the way early while you are fresh, and more soul-uplifting to have Tahoma in front of you for as much of the hike as possible.

Ending at Mowich Lake brings one final delight: what a lovely lake that is to swim in after hiking on a hot day.