Decades ago, as a young CIA analyst, President Jack Ryan, Sr. inadvertently uncovered the existence of a KGB assassin, code-named Zenith. He never found the killer.In the present, President Valeri Volodin has risen to power in the Russian republic. But the foundations of his empire are built on a bloody secret from the past, and he'll eliminate anyone who comes close to that truth.When an old friend of the Ryans is poisoned by a radioactive agent, the trail leads to Russia. And for Jack Ryan, Jr. it's time to finish what his father started . . .