Jack Ryan finds himself recruited by the CIA for his special skills: he has a tough physique from his time with the Marines and a brain for numbers from his years at the London School of Economics. Ryan works on Wall Street for a stock brokerage, doing covert operations for the government looking for possible terrorist fund transactions. When he spots an irregularity in the accounts of a Russian named Cherevin, he is sent overseas to do an audit. Upon arrival, an attempt is made on his life, and Ryan finds himself upgraded from analyst to active duty. To make matters even more complicated, his girlfriend follows him to Russia to see if he's having an affair. When they uncover an imminent nuclear attack on American soil, it's up to Ryan to get into Cherevin's building, find out the particulars of the terrorist plot, and stop it before innocent lives are claimed.