Short and Sweet
The trail starts from the Brins Mesa West Trailhead. The trail is unofficial and doesn't show up on many of the local Sedona hiking maps or the Forest Service sign post.
The rewards of this trail are spectacular views and two ruins sites; one in the best condition I've seen in the Sedona area.
From the iron sign that marks the Brins Mesa Trailhead walk up the trail 200 feet. There is (or was) no cairn but it's easy to spot a side trail. However, that day a log was placed across the trail entrance.
The path itself is quite easy to follow and it's marked with hiker cairns along the way. After crossing a wash (with grey boulders) and a red rock arroyo you will begin a climb of 450 feet. Use caution, the sand and rocks are loose. At the top you will follow the trail as it proceeds south towards a prominent red rounded rock that marks the Northern beginning of the canyon. The trail goes around the rock and into the canyon.
From here you are walking on a 15 foot wide ledge with shear walls to the east and a shear drop to the west... not a place for kids or those who fear heights.
About half-way into the canyon you will see a long shallow cave with ruins. It's possible to climb up to the ruins. As you approach the end of the canyon look down in to the north and you will see the second ruins sight - very well preserved.
At this point you have gone about 1.5 miles. But you may continue to follow the canyon ledge around the northwestern mouth. It curves around another large toe rock and goes into the canyon that contains Devils Bridge... viewable from the trail.
WARNING! Hiking and outdoor related sports can be dangerous. Be responsible and prepare for the trip. Study the area you are entering and plan accordingly. Dress for the current and unexpected weather changes. Take plenty of water. Never go alone. Make an itinerary with your plan(s), route(s), destination(s) and expected return time. Give your itinerary to trusted family and/or friends.