In Critical Mass, an action/adventure novel, Ahmad Mohammed Khan first clashes with Sean O'Rourke in 1997, when Ahmad, his three sons, and two Saudi associates smuggle drugs across the Mexican border into California to help finance terrorist operations. At that time, Sean is a sergeant in the Marine Corps on JTF-6 duty observing the border. Eight years later, Ahmad leads an attempt to smuggle two nuclear bombs into the U.S. from British Columbia. Ahmad takes Canadian rancher, Billy Deerhorn, and his family hostage and forces him to take a group of terrorists and the bombs through the mountainous Pasayten Wilderness on horses and pack mules. After a failed FBI attempt to intercept the bombs, the Secretary of Defense authorizes a military operation involving Navy SEALs to prevent the terrorists from destroying a series of dams along the Skagit River in Washington state. Now a Navy EOD tech attached to the SEAL team sent in to stop the terrorists, Sean faces the daunting task of disarming a nuclear device already set to detonate. A violent ambush on the Mexican border; the boarding of a Ukrainian ship in the south Pacific by U.S. Navy SEALs; a hostage rescue operation in Canada; an ill-fated FBI SWAT operation; an assault by Navy SEALs on a terrorist-held dam--the story offers plenty of action, interesting characters, and a chilling plot that could appear in real news headlines tomorrow.