Beneath the ancient arches of the Pont du Gard, a chilling pattern of annual murders has gone unsolved for years—until detective Grace Whitmore arrives. As she traces instinct, reflection, and hidden histories across centuries-old stones, Grace discovers that every pause, every gesture, every micro-pattern holds a clue to the killer’s inevitable path. With time running out, she must anticipate the next move before the river claims another victim. A labyrinth of secrets, shadows, and human behavior unfolds in this gripping European mystery—one that will lead Grace from the sunlit bridges of southern France to the crowded, enigmatic streets of Venice, where a stranger in the Piazza San Marco will set the stage for her next encounter.