Immediately start grinding up a wide singletrack high above the creek. It can be tough since you've had no warm-up and it's pretty consistent for over a mile and fully exposed to the sun. You'll pass a gate on the left (which heads over to Red Dirt Trail), and shortly thereafter to a historic (and photogenic) barn.
Pass that, head downhill to a bridge which connects to the Madhouse Trail, which would take you back to the trailhead.
For maximum fun though, continue up the Mad Creek Trail on the left side of the creek for another mile or so through superb aspens and meadows. There are a couple pullovers next to the creek which are great for a snack. It's a smooth, skinny singletrack in this area, and ends all too quickly at the Mount Zirkel Wilderness boundary. Bikes are not allowed in any wilderness zone in the USA. Turn around and enjoy the descent!