Thunderhead

Thunderhead is a 1999 thriller novel published by Grand Central Publishing. Although it is technically a standalone novel, it introduces Dr. Nora Kelly, who later appears as a supporting character in the Agent Pendergast series, and features Bill Smithback, a longtime Pendergast associate.

Plot Summary
"'Nora Kelly, a young archaeologist in Santa Fe, receives a letter written sixteen years ago, yet mysteriously mailed only recently. In it her father, long believed dead, hints at a fantastic discovery that will make him famous and rich—the lost city of an ancient civilization that suddenly vanished a thousand years ago. Now Nora is leading an expedition into a harsh, remote corner of Utah's canyon country. Searching for her father and his glory, Nora begins t unravel the greatest riddle of American archeology. but what she unearths will be the newest of horrors...'"-Publisher's synopsis

Continuity

 * Bill Smithback appears as a main character, fresh off the success of his books, the in-universe versions of Relic and Reliquary. By the time of the events of The Cabinet of Curiosities, he had published a book about the Quivira expedition called Thunderhead.
 * Nora Kelly returned as a major supporting character in the Agent Pendergast series, starting with The Cabinet of Curiosities.