The Pacific Northwest is beautiful, prosperous, and dangerously exposed to a fault capable of reshaping the region in minutes. In Faultline: Cascadia Megathrust, John S. Pritchett follows scientist and professor Josh Cooper as he confronts one of North America's most consequential natural hazards: the Cascadia Subduction Zone. A year after the events at Changbai Mountain, Josh is still trying to rebuild an ordinary life with his wife, Emily, their two sons, and a newly adopted dog named Jasper. But when the University of Washington asks him to lead a major earthquake preparedness initiative, the quiet life he is rebuilding collides with a responsibility he cannot ignore. Scientists cannot predict when Cascadia will rupture. They do know that a full-margin magnitude-nine earthquake could produce prolonged shaking, destructive tsunamis, landslides, liquefaction, infrastructure failure, widespread displacement, and enormous economic losses across the Pacific Northwest. The question is not how to stop the earthquake. It is how much devastation can be prevented before it happens. Josh and his colleagues push beyond traditional disaster response toward a new model built on mitigation, preparedness, and resilience. Their work reaches from seismic monitoring and offshore sensors to vertical evacuation, stronger infrastructure, emergency supplies, public education, funding, and coordination among local, state, and federal agencies. The challenge soon moves beyond science. Josh must convince governors, federal officials, university leaders, and ultimately the President that spending money before disaster strikes can save lives and reduce the far greater costs of recovery. Then a magnitude 6.3 earthquake strikes near Olympia. It is not the Cascadia megathrust, nor proof that the Big One is imminent. But damaged roads, power failures, landslides, and disrupted communities transform an abstract warning into a vivid demonstration of regional vulnerability. Preparedness is no longer theoretical. Blending geoscience, public policy, family drama, leadership, and disaster suspense, Faultline: Cascadia Megathrust asks what happens when a society knows a catastrophe will eventually come but cannot know when. The fault cannot be controlled. What can change is how ready we are when it moves.