Johnny Ross works for Chicago mobster Peter Ross, his brother. In April 1968 Johnny Ross escapes two attempts on his life and flees to San Francisco, where he is placed in protective custody by politician Walter Chalmers, who hopes to use Ross to further his own national aspirations. To protect Ross, Chalmers asks the SFPD to assign Detective Lieutenant Frank Bullitt and his partners, Sergeants Don Delgetti and Carl Stanton, to guard him at a flophouse near an overhead freeway. It looks like a simple assignment, but at 1 AM the next day it all goes awry in a blast of a shotgun, leaving Stanton and Ross fighting for life at San Francisco General. Bullitt gets what information he can, but breathing down his neck is the angered Chalmers who vows to ruin Bullitt’s career should Ross die. Bullitt gets a break when the gunman appears at the hospital to finish off Ross, and Bullitt gets a good look at him; now Bullitt must smoke out the gunman and his backup man before Chalmers carries out his threat, leading to a high-speed pursuit, a fiery crash at a gas station, and a fingerprint check that leads to a stunning discovery about Ross, and about a couple staying at a swanky hotel in San Mateo.