In the fourth and final horrific adventure in the award-winning Monstrumologist series, Will Henry encounters unprecedented terror, a terror that delves into the depths of the human soul.<br><br>Will Henry has been through more than seems possible for a boy of fourteen. He's been on the brink of death on more than one occasion, he has gazed into hell - and hell has stared back at him, and known his face. But through it all, Dr. Warthrop has been at his side.<br><br>When Dr. Warthrop fears that Will's loyalties may be shifting, he turns on Will with a fury, determined to reclaim his young apprentice's devotion. And so Will must face one of the most horrific creatures of his monstrumology career - and he must face it alone.<br><br>Over the course of one day, Will's life - and Pellinor Warthrop's destiny - will hang in the balance. In the terrifying depths of the Monstrumarium, they will face a monster more terrible than any they could have imagined - and their fates will be decided.<br><br>"Beyond a simple finale, this is a brave statement about the duplexity of good and evil, and the deadly trap in which all of us are snared" (<i>BOOKLIST </i>, starred review) .
