Thunderhead is the story of a scientific expedition in the deserts of the American Southwest. A team of scientists is looking for the ancient city of Quivira, the mythical capital of the Anasazi Indians, one of the most secretive and least understood of all Native American tribes. Legend has it that Quivira was the repository for all of the tribe's treasures — gold that countless Spanish conquistadors lost their lives searching for. What the legends don't mention is why the Anasazi vanished. Unknown to the expedition's leader, Nora Kelly — an archaeologist whose father vanished 15 years earlier looking for Quivira — the evil that befell the tribe is still around.

Nora, along with a group of scientists, adventurers, and the daughter of the director of the Santa Fe Archaeological Institute, starts to follow a tenuous map left by her missing father, the early conveniences are quickly forgotten. During the perilous journey, the team is dogged by two horrifying creatures that will do anything to make certain the band doesn't find the city. By ferryboat, by raft, and finally, by horse, the team wanders deeper and deeper into southern Utah's deadly maze of canyons, each step taking them closer to a place where nature's fury and an ancient curse wait to destroy anyone who comes too close.

On the verge of the greatest discovery since King Tut's tomb, Nora finds her group falling apart — derailed by the hardships of their quest and conflicting personal agendas. It's not long before their horses begin to die mysteriously, and then some of the scientists. Cut off from the outside world, with friends and coworkers dropping around her, Nora must race to save her own life. She may have figured out what killed the Anasazi - just in time to find it's killing her too.