Wilderness Patrol fficer Pamela Tate, scouting in the mountains of Washington, sees and touches a ground squirrel in the dusty path, blood trickling from its mouth. Forty-eight hours later she lies dead at her campsite, covered in mysterious welts and bruises. Across the lake, a boisterous camping party falls silent as they watch each other sicken and die in agony. A killer is loose. It has a foreign name. Yersinia Pestis. Plague. An unknowing nation harbors the deadly evil in its midst. While a few embattled survivors race to save the country, perhaps the world, the grim invader hides in a mother’s sigh, a child’s laugh, a lover’s whisper. Nothing can stop the death ride of . . . The Fourth Horseman.