The Latenight Trail runs near the base of the mountains on the southwest portion of Red Rock NCA. They call it the Latenight Loop; not sure why as you need to run one of the other trails to make a loop.
Start from the Latenight Trailhead and run west, skirting Hwy 160. This part of the trail is less exciting than the rest - "gotta pay if you wanna play" I always say, it's a Vegas thing.
At the tunnel that connects 3 Mile Smile
to the south, steer north - this is where the fun begins. You'll enjoy the fruits of your labor for a good bit of downhillish fun. Enjoy the smooth, winding trail while you can for soon you'll be treated with some of the pretty rocky sections. If it's hot, relish the few shade spots, or just run when it's cool.