Colorado Parks & Wildlife Research Library

Amy and Dan Cahill have been located once again, this time in the company of the notoriously unreliable Alistair. Spies report that Amy and Dan seem to be tracking the life of one of the most powerful fighters the world has ever known. If this fearsome warrior was a Cahill, his secrets are sure to be well-guarded.

At Princeton University, a famed geneticist dies inside a biohazard lab. In Rome, a Vatican archaeologist is found dead in St. Peter's Basilica. In Africa, a U.S. senator's son is slain outside a Red Cross camp. The three murders on three continents bear a horrifying connection: all the victims are marked by a Druidic pagan cross burned into their flesh. The bizarre murders thrust Commander Gray Pierce and Sigma Force into a race against time to solve...

When the NSA invincible code-breaking machine encounters a code it connot break, the agency calls in head cryptographer, Susan Fletcher. What she uncovers sends shock waves through the corridors of power. Caught in a tempest of secrecy and lies, Fletcher battles for her country, her life and the life of the man she loves.

Amy and Dan Cahill's quest to find the million dollars takes them to Vienna, where they must outwit their power-hungry relatives as they seek to solve a clue involving Mozart.

"Are some secrets better left buried? As Amy and Dan track the next clue to a remote corner of the world, they make shocking discoveries about the source of the Cahills' power and the mystery of their parents' deaths. And as the threat of the mysterious Madrigals grows real, one of the clue-hunters makes the ultimate sacrifice. Amy and Dan have to decide how much they're willing to risk, and what they are fighting for. Can they avenge their parents...

Amy and Dan Cahill face their greatest challenge on their quest to find the thirty-nine clues, but in order to discover the secrets of their lineage they will have to make a choice that could impact the world's future.

Former Justice Department operative Cotton Malone has hunted priceless treasures and confronted ruthless adversaries around the world. Now, a grave threat to the very foundation of our country has summoned him home to America.

After being taught in a boarding school run by whites that Navajo is a useless language, Ned Begay and other Navajo men are recruited by the Marines to become Code Talkers, sending messages during World War II in their native tongue.

It's no longer a game. The body count is rising. Shaken by recent events, Amy and Dan flee to a distant land and trace the footsteps of their most formidable ancestor yet: a military leader of mythic proportions. Yet just as the siblings begin to master the art of ancient warfare, they confront a dangerous enemy that can't be felled with a sword: the truth. With the stakes higher than ever, Amy and Dan uncover something so devastating it changes everything...

Chronicles the first Vesper attack on Jan van Eyck's altarpiece at Ghent in the 1600s, then jumps to WWII and young Grace Cahill's desperate bid to save the masterwork from the Nazis.