Sent to investigate a problem aboard a nuclear submarine, Steve finds himself beset by vicious sharks. He evades them and reaches the safety of the submarine, only discover that his problems have gotten worse: Morgan Grayland, a rogue Naval officer, has captured the vessel and intends to become a pirate! And since the sharks obey Grayland, Steve will have to find a way past them to defeat the madman.
Admiral Prescott, aware his nuclear sub has fallen into criminal hands, sends a fleet of ships to destroy it. On board, the would-be pirates squabble over control, and the winner, a man named Parker, informs the Navy that he will destroy Charleston, S.C. if Prescott does not withdraw his fleet. Unwilling to risk a nuclear attack by his own ship, Prescott leaves Steve to find his own way out of this mess!
Oscar sends Steve to Kennedy Space Center to assist with the link-up of two satellites. These operations interfere with the criminal plans of Gordon Shanks, who intends to steal part of the United States' newest missile defense system, so he sends an assassin to kill Steve Austin.
Gordon Shanks's assassin has failed, so he must devise a new plan. And he does: he kidnaps Melissa McGrath, daughter of Kennedy mission director Dave McGrath, so that he can pressure McGrath to sabotage the mission and murder Steve. But Steve foils the plan and McGrath confesses - and Steve vows to recover Melissa and end Shanks's ambitions for good.
An eager anthropologist comes by the location of Bigfoot, the animal brought to the Earth by aliens. Bigfoot is awakened from his hibernation and causes havoc. Oscar assigns Steve and Rudy to catch him. When they grab him he's numb by having fallen into an icy river and Rudy analyzes him and finds the creature is undergoing an amazing transformation.
A mechanical fault leaves a group of students stuck in a mountain tramway, directly in the path of a cyclone. Steve and two other people go to their rescue, but one of them isn't what he seems. On the run from the authorities, Nash betrays Steve and leaves him unconscious in a ditch with time running out.
Rand Hendricks, owner of the roller derby Rockets is also a spy. He intends to sell O.S.I. secrets for $10,000,000, so Steve goes undercover as a member of the team to stop him. But Hendricks learns who Steve is, and sends him on a wild goose chase, leaving the critical data unprotected.
Chances in the lunar orbit cause big problems on Earth. Sent to investigate, Steve quickly learns that scientist Charles Leith has left the asteroid where mission control believes him to be and gone to the moon, where he has altered its orbit!
Steve arrives on the moon, but Leith and his henchman capture the agent, and force him to help them mine a new energy source they call dilanthium. If Steve refuses to help them, they'll use nuclear devices that will further alter the Earth's orbit, causing more havoc!
After criminals penetrate O.S.I. in search of atomic secrets, Oscar pairs Steve with Joan and gives them a cover as newlyweds exploring the country in an R.V. that contains special equipment including an advanced power source. Unfortunately for them, the criminals have pierced their cover and intend to turn the tables on them and steal their special vehicle.
Jenny Fraser disappears while piloting a plane equipped with a new form of anti-radar stealth technology. Steve has a personal interest in this one; he was seeing Jenny socially. Soon enough, he learns that an engineer might have given information about the plane to Wilfred Damien, a man known for selling military secrets to the highest bidder.
Steve must win the trust of an exiled Russian scientist, Viktor Cheraskin, who has invented a device to catch soldiers without injuring them. The man is hiding with an air show crew. Just when he has approached Victor, Russian agent Edmund Dmitri contracts Victor with the news that he has the scientist's wife and will kill her unless Victor hands over the schematics.
Somehow, a routine orbital test hurls Steve six years into the future. On his return, government agents arrest him; when he disappeared, they believed he defected to the Soviets who brainwashed him into believing he'd traveled in time. Steve must figure out how to clear his name so that he can then figure out how to return to the correct time.
Steve thought he destroyed the renegade Russian Venus probe more than a year ago, but it has returned, deadlier than ever. And the person who controls it demands Oscar hand over several nuclear warheads, or he'll unleash the machine on innocent people. Steve barely defeated the last probe. How will he handle this even tougher version?
Steve tries various tricks to stop the new Death Probe, including a ram made of a tough new allow. But nothing works until he manages to trick the machine into a large pit. Before he can fill the pit with an acid to destroy the probe, it begins to drill a tunnel towards a nearby city. Now how will Steve stop it?
Steve searches for a downed satellite and learns that it fell on a concealed island inhabited by the descendants of alien explorers. One of their number will help him retrieve the orbiter if he helps her in return: her people have no resistance to Earth-evolved microorganisms, and so she wants an experimental serum under development in exchange for the satellite.
A microdot containing valuable information is hidden inside a Romanesque painting of a Madonna. Steve helps a Countess retrieve the chip by stealing the painting. She turns around and sells the microdot to criminal mastermind Chilton Kane! When Oscar and Steve learn that they have been duped, Steve sets out to retrieve the painting before its loss embarrasses the United States.
Steve catches glimpses of a dark figure who looks like him. Rudy worries for Steve's health, but a parapsychologist offers a different explanation: when Steve was technically "dead" just after his accident, his spirit detached from his body and now roams the ether, trapped between life and deah. It intends to make sure it can continue on, and there's only one way to accomplish that.
O.S.I. communications chief Joe Canton stands accused of passing secrets to an enemy, but Steve can't believe it. He tries to read the computer core containing the evidence, but it self-destructs. His only remaining clue is an outside access from an unlikely source: Datamate, a computer dating service owned by Emily Patterson. As Steve investigates further, his enemy takes steps to stop him.
Steve joins forces with Emily Patterson. They know who their real enemy is, now - a self-aware computer. It first hires a hitman, but Steve evades that hazard. Then Steve finds himself sent to a mental hospital. Somehow, the police computers have listed him as a dangerous psychotic. While Steve tries to escape the hospital, his machine opponent decided to "pull the plugs" of its human enemies, starting with Emily.
Santos, a terrorist, steals self-guided missiles from the United States, and a mobile missile launcher from the Soviet Union. Oscar dispatches Steve to recover the stolen missiles, while KGB general Noorbukov sends his own agent, Andrea Mestrova. But there's a catch: while Steve only wants his government's missiles, Andrea has orders to recover both launcher and missiles - and to kill Steve Austin if he tries to prevent it!