At the Saint Ignatius Orphanage, a rebellious boy named John Rossi refers to himself as "Simon Templar" and leads his fellow orphans in a bold bid to run away. He tries to bid farewell to a girl named Agnes with a kiss, but their escape plan goes tragically wrong when she falls from a balcony to her death, a moment that haunts him as he grows up.
As an adult, Simon Templar [Val Kilmer], a professional thief who moves between aliases with a chameleon’s ease, earns his nickname by adopting saints’ names as his covers. He steals a microchip from a Russian oil company during a high-profile rally for its owner, Ivan Tretiak, a billionaire oligarch and former Communist Party boss rallying support against Russian President Karpov. When Simon is caught by Tretiak’s son Ilya but escapes with the microchip, Tretiak hires him to steal a revolutionary cold fusion formula discovered by Emma Russell, an American electrochemist working at Oxford. Tretiak’s motive is chillingly clear: use the breakthrough to monopolize the energy market during a looming oil shortage in Russia, and then murder Simon to keep the money and power for himself.
Using the alias "Thomas More," Simon poses as a Boer traveller to seduce Emma and steals her groundbreaking formula. Yet as he grows fond of her, he contemplates backing away from the theft. Tretiak’s threat to kidnap Emma rescripts that choice, and Simon ultimately seizes the formula after a one-night stand. Tretiak soon realizes the formula is incomplete and orders Ilya and his henchmen to eliminate Simon, who narrowly escapes. He returns to Russia to demand payment from Tretiak, going so far as to disguise himself as Tretiak to press his claim for what is owed.
A heartbroken Emma reports the theft of her work to Inspectors Teal and Rabineau of Scotland Yard, who reveal that Simon is a wanted international thief. Emma eventually tracks him down to a Moscow hotel, only to be arrested with Simon by Tretiak’s men; they escape together and evade capture by seeking shelter with a prostitute and her family, then receive help from Frankie, a spiv who guides them through sewers toward the U.S. embassy. When Ilya and his men close in, Simon sacrifices his safety to let Emma reach the embassy, and later escapes by triggering a car’s gas tank and leaving Ilya badly burned.
From Tretiak’s office, Simon discovers a plan to sell the incomplete formula to Karpov and frame him for wasting billions on useless technology, thereby using the scandal to crown himself president. Emma completes the formula, which Simon delivers to Tretiak’s well-meaning physicist Dr. Lev Botvin, whose device confirms the formula’s validity. With Botvin’s cold fusion reactor proof, Simon infiltrates the Kremlin and alerts Karpov to Tretiak’s scheme, though they are briefly captured by Tretiak loyalists. In a climactic Red Square gathering, Tretiak denounces Karpov, but Botvin’s reactor is activated, exposing Tretiak as a fraud. Tretiak and Ilya are arrested, and their scheme is revealed to have caused Russia’s oil shortage by hoarding fuel beneath their mansion.
Reuniting with Emma, Simon returns her formula and they begin a discreet, evolving relationship. Emma presents her discovery to the world at a press conference, while Simon attends in disguise, slipping away when Teal and Rabineau spot him. A news broadcast later reveals that $3 billion has been donated to the Red Cross, the Salvation Army, and UNICEF, implying that Simon—the man who once seized Tretiak’s accounts—has anonymously funded a non-profit foundation led by Botvin to advance the cold-fusion technology for the good of all.
