Alex Rider (Alex Pettyfer) is a normal teenager who lives with his uncle, a nondescript bank manager... or so it seems until his uncle—Ian Rider (Ewan McGregor)—disappears under mysterious circumstances. Alex soon learns that his uncle was a spy for Britain's secret intelligence service MI6. Recruited by Mr. Blunt (Bill Nighy) and Mrs. Jones (Sophie Okonedo) of Special Operations, Alex discovers that by encouraging his hobbies, Uncle Ian had actually prepared him for a career in espionage. With Alex's skills in languages, scuba diving, mountaineering and martial arts, he has all the attributes of a perfect spy. His age not withstanding, Alex endures two weeks of MI6 training. Then, armed with special gadgets to help him, he embarks on his first mission.

Billionaire Darrius Sayle (Mickey Rourke) is donating a free Stormbreaker mega-computer to every school in Britain. But is there more to his generosity than meets the eye? MI6 sends Alex in to investigate. Going undercover as the winner of a computer competition, he infiltrates Sayle's heavily-guarded compound. He meets the tycoon's sinister sidekicks—vixen publicist Nadia Vole (Missi Pyle) and the disfigured mute Mr. Grin (Andy Serkis)—and gets to test out the impressive and secretive Stormbreaker computer...