LATER IN THE WEEK, Adam's father, Ben Teller, takes me down the other major branch of the canyon—an equally spectacular prong known as Canyon del Muerto. We're on horseback, clopping through thickets of chamisa, finding shortcuts through fields whose owner invariably seems to be Ben's aunt or cousin or nephew. "Don't worry," Ben assures me. "We're all related!"

I'm riding an old nag who doesn't seem to like me much. We turn into a side canyon, and as the walls grow tighter, she fiendishly speeds up while hewing tightly to the rock. Perhaps she's hoping to knock me off, or at least give my thigh a long, hard pinch on the sandstone while she simultaneously gives herself a luxurious loofah rub.

On this particular day, Ben is wearing a feed cap, blue jeans, and, inexplicably, a fancy pair of tasseled loafers. He's a stocky, amiable guy in his late sixties with thick glasses. Ben lives alone down in the canyon and is one of the only people who stays here year-round. (The icy winters can be brutal.) He drives an old Massey Ferguson tractor and has a cabin set on family land at an amazing spot inside Canyon del Muerto called Antelope House (after which Adam named his company). It's the site of an Anasazi ruin constructed in a.d. who-the-hell-knows, a chinked-rock pueblo that once had as many as 91 rooms and several kivas.

Because Ben lives in such a remote place, he sent word ahead for me to bring beans and beer, his usual standbys. I got the beans but failed him on the beer, since Chinle, like the rest of the reservation, is dry. "Dat's OK," he said, trying not to telegraph his disappointment. "Next time, though, bring beer."

Despite my horse's diabolical nature, I decide that horseback really is the best way to see the canyon. Ben and I can get to places that Adam's 4x4 can't, and the pace of a walking horse is just about right for taking in the ever-shifting angles and plays of light. As we ride together, Ben tells stories of the old days, shows me where he used to go swimming at a natural mudslide that formed every spring when the snowmelt brought running water, shows me the place where some Hollywood western was filmed in the fifties (Canyon River, he thinks the title was). He remembers watching fellow tribesmen, all painted for battle, hurling papier- mâché boulders down onto the actors. "I know it sounds weird," Ben says with a chuckle, "but I was rooting for the white guys!"

At a place called Standing Cow Ruin, Ben points out a remarkable pictograph stained on the wall. It's a realistic rendering of a long train of cavalrymen, wearing flat-brimmed hats, carrying lances and muskets, and riding pinto horses into battle. The ominous figures look like horsemen of the apocalypse, their capes clearly emblazoned with crosses.

"Those are Spaniards," Ben says. "From your town. Santa Fe."

The Diné inked these haunting images onto the walls to memorialize a painful event—perhaps the only occasion on which the Spanish successfully invaded this Navajo refuge. In January 1805, a force of nearly 500 Spanish soldiers marched all the way from New Mexico's capital, killing Navajo warriors by the score and collecting prisoners as they rampaged through the canyon's meandering course. In Canyon del Muerto, not far from where these images were painted, the Spanish troops were surprised to hear the shrill voice of a Navajo woman shouting strange invectives at them. "There go the men without eyes!" the voice screamed. "You must be blind!"

Puzzled, one of the soldiers climbed up the talus and spotted a group of more than 100 women and children crouched in a high recess of the canyon wall. Another soldier began to crawl his way up the steep wall with the notion of rounding up prisoners. When he crossed the threshold of the cave, a Navajo woman wrapped her arms around him and dashed for the precipice; the two figures, locked in a desperate grip, plunged several hundred feet to their deaths.

From the canyon floor, the soldiers began to ricochet bullets off the roof of the cave. Eventually everyone was killed but an old man, who would relate the story to other Navajo. More than 150 years later, the victims' bones were still lying on the cave floor when archaeologists examined the site.

Today the spot is widely known as Massacre Cave. But, Ben tells me, the Navajo have their own name for it: The Place Where Two Fell Off.