When a woman is beheaded in a park outside Rome and her six-year-old son goes missing, the police unit assigned to the case arrests the woman’s husband and awaits his confession. But the city’s Chief of Major Crimes has his doubts and assigns two of Italy’s top analytical minds to the case: Deputy Captain Colomba Caselli, a fierce, warrior-like detective still reeling from a horrific mass killing she survived, and Dante Torre, a man who spent his childhood trapped inside a concrete silo. Fed through the gloved hand of a masked kidnapper who called himself 'the Father,' Dante emerged from his ordeal with crippling claustrophobia but, also, with an unquenchable thirst for knowledge. All evidence suggests that the Father is back at work and wants a reunion with Dante. But when Colomba and Dante begin unraveling the truth, they find themselves wanted for murder. Now Dante and Colomba must travel down a number of dark tunnels, both literal and figurative, as they confront the question that may solve it all: what lies beneath the water in a remote Italian quarry? And what might that revelation mean for ten children who have recently gone missing?