Veteran CIA officer Peter Devereaux (Pierce Brosnan) supervises a young operative David Mason (Luke Bracey), and chides him for becoming intimate with a local woman. Relationships can be used against an agent, he says laying out a scenario forcing an agent to choose between the job and someone they love. Subsequently, in a mission to protect a US Ambassador in Montenegro. Devereaux, wearing Kevlar, impersonates the ambassador in a public square, drawing the fire of an assassin. Mason disobeys Devereaux's orders not to fire as the crowd is too close, and in shooting the assassin, Mason accidentally kills a child.
Issa Karpov (Grigoriy Dobrygin), a political refugee from Chechnya who has been tortured by Russian security forces, enters Hamburg, Germany, illegally.
Teresa "Terry" Doolittle (Whoopi Goldberg) transfers funds for the First National Bank in Manhattan, New York. She does not quite fit with the bank's corporate image, despite being a good employee and popular with her co-workers. She is often chastised by her no-nonsense boss James Page (Peter Michael Goetz).
Agent Cody Banks (Frankie Muniz) attends summer camp, actually a secret facility for training CIA teenage agents. When a group of CIA soldiers attempt to abduct head counselor Victor Diaz (Keith Allen), Cody helps him escape, mistaking the CIA operation for a training exercise. The director informs Cody that Diaz stole disks containing plans for a secret mind-control device, and sends Cody to recapture him.
"Darn Cat" or "DC" is a wily, adventurous Siamese tomcat who lives with two young women, suburbanite sisters Ingrid "Inkie" (Dorothy Provine) and Patricia "Patti" Randall (Hayley Mills), whose parents are traveling abroad at the time of the story.
Secret agent WD-40 Dick Steele (Leslie Nielsen) has his work cut out for him. Along with the mysterious and lovely Veronique Ukrinsky, Agent 3.14, he must rescue the kidnapped Barbara Dahl and stop the evil genius, a General named Rancor (Andy Griffith), from seizing control of the entire world.
Harriet M. Welsch (Michelle Trachtenberg) is an eleven-year-old sixth grader and a young spy/writer who is best friends with Simon "Sport" Rocque (Gregory Smith) and Janie Gibbs (Vanessa Lee Chester). She lives a privileged life with her parents and her nanny, Katherine "Ole Golly" (Rosie O'Donnell), who's the only person who knows all the things that Harriet has been snooping on. Harriet and her friends are enemies with mainly Marion Hawthorne (Charlotte Sullivan). For a while, Harriet lives life very well with being a spy and having fun with Golly.
CIA analyst Douglas Freeman (Jake Gyllenhaal) is briefing a newly arrived CIA agent in a square in an unnamed country in North Africa (filmed in Marrakech), when a suicide attack kills this agent and 18 other people. The target was a high-ranking police official, Abbas-i "Abasi" Fawal (Yigal Naor), who acts as a liaison for the United States and whose tasks include conducting interrogations and overseeing the application of techniques amounting to torture. Fawal escapes unscathed.
Alicia Huberman (Ingrid Bergman), the American daughter of a convicted Nazi spy, is recruited by government agent T. R. Devlin (Cary Grant) to infiltrate an organisation of Nazis who have moved to Brazil after World War II. When Alicia refuses to help the police, Devlin plays recordings of her fighting with her father and insisting that she loves America.
Alex Rider is a 14-year-old schoolboy who lives with his uncle Ian and their housekeeper Jack Starbright. Ian is supposedly a bank manager and is, much to Alex's regret, often away from home. One day, Alex is told that his uncle has died in a car crash, but quickly discovers that his uncle was in fact a spy working for MI6 and that he was killed by the assassin, Yassen Gregorovich.
Samir Horn (Don Cheadle) is an Arabic-speaking Sudanese-American and devout Muslim. His Sudanese father was killed by a car bomb when he was a child. As an adult, Horn is first seen operating as an arms dealer. While negotiating a deal with Omar (Saïd Taghmaoui) in Yemen he is arrested and thrown into a Yemeni jail. Later, Samir and Omar become friends and when Omar's people arrange an escape, he takes Samir with them.
Bartholomew "Barley" Scott Blair (Sean Connery), the head of a British publishing firm, is on a business trip to Moscow. He attends a writers' retreat near Peredelkino where he speaks of an inevitable New World Order and an end to tensions with the West. Attentively listening is a man called Dante (Goethe in the novel) (Klaus Maria Brandauer), who wants to be convinced that Barley means what he says. It transpires that Dante is in fact a renowned physicist who has secretly written a manuscript detailing the Soviet Union's nuclear missile capabilities.
Thomas "Babe" Levy (Dustin Hoffman) is a history Ph.D. candidate and avid runner. Levy is researching the same field as his father, who committed suicide after the Communist witch hunts of the Joseph McCarthy era ruined his reputation. Babe's brother Henry (Roy Scheider), known as "Doc", presents himself as an oil company executive but is really a government agent, involved in an elaborate network of couriers who transport diamonds stolen during World War II from wealthy Jews seeking to flee Germany, which are then sold on world markets for the secret benefit of fugitive Nazi war criminal Dr. Christian Szell (Laurence Olivier). Szell, a dentist who tortured Jews in a concentration camp, escaped capture and is now living off the diamond sales as a fugitive in South America (echoing real life Nazi war criminal Josef Mengele).
A Russian organized crime group takes possession of an advanced bio-chemical weapon from Korea with the help of a corrupt Korean scientist, and two special agents are the world's only hope to stop them. One is a veteran domestic secret agent named Ahn Soo-ji (Kim Ha-neul) who is a master martial artist and fencer. The other is a rookie international agent named Lee Jae-joon (Kang Ji-hwan) who's foundation in analytical work, rather than field work, gets him into trouble when he consistently goofs up on the job. The two agents have an ill-fated relationship, when coincidentally they are dating and don’t know each other's secret identities. Ironically, the passion between them turns to madness, as the lies and secrets between them build until they nearly kill each other. They only thing they can trust is the fact they love and hate each other. The tension builds as they attempt to work out their relationship, while working behind each other's backs, unknowingly on the same mission to save the world.