Detective Grant Starr and his buddy Detective Ralph Bensen took the day off to catch a Giants' game, but their plans are cut short when a lunatic starts shooting people from the top of a twelve-story hotel. The shooter is crazy, but he's also crazy-good with the sniper rifle. The gunman's found dead and Grant has no idea who he is or why he killed nine people, apparently at random. When two more are murdered the following night, Grant finds a thread connecting the eleven killings. Unfortunately, he's up against a well-funded fanatical eco-terrorist with a gang of hired mercenaries. After a building housing giant pumps in the San Joaquin Delta is blown up with a fertilizer bomb, Grant chases the gang into the foothills, then to the Hetch Hetchy Valley in Yosemite National Park. The unthinkable happens: the O'Shaughnessy Dam at Hetch Hetchy is attacked with multiple bombs. It fails in a most spectacular way and a sixty-foot-high wall of water is sent hurdling down the mountain... Can Grant and his team stop what would be the worst U.S. disaster since 9/11?