The cache is a small ammo box.
Park at the Lyon's Creek trailhead. The cache is up the Lyon's Creek trail. Bring mosquito repellent. The cache is outside the Desolation Wilderness, so you don't need a permit to find the cache, but if you plan to go further up the trail, fill out a permit at the trailhead. Snow will most likely make this cache inaccessible until late May.
If you like wildflowers, you'll like this trail. The quantity and variety of flowers is amazing.