It starts, as before, with a motionless body -- dead? alive? -- underwater. This time the immobile figure is Aaron Cross, a medically enhanced hunter/killer in the same U.S. black-ops program that spawned Jason Bourne.

He emerges from an icy Alaska lake to participate in a hide-and-seek exercise testing his superhuman stamina and amped-up brainpower. In a white-knuckle sequence orchestrated to magnificent effect by cinematographer Robert Elswit, Cross (Jeremy Renner) leaps chasms and outmaneuvers a predatory wolf pack.

When he asks another agent whether it's common for wolves to pursue human quarry, the man replies, "They don't think you're human."

He is and he isn't. As with its chilly, intelligent predecessors, "The Bourne Legacy" follows a field agent whose physiology has been re-engineered as a perfect violence engine, but whose emotions remain preoccupied with nagging moral issues of right and wrong.

Cross, known as No. 5 to his distant overseers, is kept on a short leash. He carries only a few days' supply of the ultra-amphetamines that provide his killer edge. When a security breach threatens to expose the clandestine program, management terminates it with ruthless efficiency, live assets and all. Cross, whose participation in the program was mostly unwitting, aims to shut down the shadowy spymasters before his prescriptions run out.

The Bourne franchise lost valuable assets when Matt Damon and director Peter Greengrass withdrew from the series, but this fourth installment proves their loss was merely a flesh wound.

Tony Gilroy, the screenwriter for every installment, steps confidently to the director's chair. Gilroy unravels this thriller in parallel time with Jason Bourne's score-settling trip to New York City. Reports of his exploits filter in through the media, while players from earlier chapters (Albert Finney, David Straithairn, Joan Allen) mingle with new CIA blackguards (principally Stacey Keach and Edward Norton, who calls the program "morally indefensible and absolutely necessary").

This time the audience surrogate/romantic interest is Rachel Weisz, playing a genetic researcher who has no options but to go on the run with Renner.

Now in charge of both the script and the camera, Gilroy maintains cool control of the narrative, ratcheting up the tension along the way toward startling bursts of excitement. He can turn a room full of D.C. bureaucrats and video monitors into a pressure cooker of anxiety, rip up the screen with a chilling lone-shooter massacre, or kick out the jams with a high-impact 8-minute motorcycle chase through traffic-choked Manila. "The Bourne Legacy" makes the most of its inheritance and sets the stage for a long, rich genealogy to come. • 612-673-7186