A Navy destroyer steams toward disaster in the waters off North Korea. While on a layover in Okinawa, Harm reunites with his former partner, Lt. Kate Pike, to explore the mysterious murder of Lt. Mason, a computer weapons specialist. On a helicopter flight to Mason's destroyer, Kate and Harm meet Mason's replacement, Lt. Commander Gino Campisano. Like Mason, Gino is one of only two experts in the use of Ares, a cutting-edge navigation and weapons system. To Kate's chagrin, her ex-lover, Commander Dennis Brockman, is also working on the case. As she later confides to Harm, their relationship ended badly when Kate rebuffed Brockman's marriage proposal. During war games in the Sea of Japan, the Ares software program suddenly takes over the destroyer's weapons system and shoots down an approaching Navy jet, whose pilots eject to safety. Minutes later, the crew discovers Ares is also overriding all communication and navigation controls. Harm narrowly manages to rescue Meg, whose helicopter must skim the water to avoid being shot out of the sky. Meg quickly determines that someone has programmed Ares to take over the destroyer, sail it toward a North Korean port, and destroy any U.S. jets attempting to stop it. Clearly, the North Koreans plan to seize the ship and its top-secret hardware. As the captain prepares to scuttle the boat rather than surrender, Harm and Meg realize Gino is a double agent who murdered Mason so he could come aboard and re-program Ares. When he's found out, Gino takes Brockman hostage, but Harm fatally shoots him and Brockman is released. Harm finds a computer disk in Gino's pocket, which allows Meg to get Ares back online and turn the ship around before the North Koreans can board it.