Working for the FBI, cryptanalyst and agoraphobe Salem Wiley vows never to return to the conspiratorial underworld her mother revealed to her. Until fieldwork draws Salem to an Ireland farm where a curious discovery has been unearthed: a near-perfect replica of Stonehenge in miniature--except for one extra stone engraved with the word mercy.

When seven-year-old Mercy Mayfair, a child in Salem's family's care, is kidnapped, Salem knows it's more than an unsettling coincidence. Mercy's centuries-old lineage holds the key to understanding the greatest Neolithic mystery of the ages. A dangerously patriarchal society, just as ancient, will kill to solve it.

As Salem follows a serpentine trail of clues and ciphers, the clock is ticking and her fears are escalating. Because the only way to save Mercy is for Salem to crack the unbreakable code of Stonehenge first.

Revised edition: This edition of Mercy's Chase includes editorial revisions.