US intelligence says there's something going on in Russia. While their land forces have been decimated by corruption and incompetence, the Navy seems to be pouring money into some secret project. 

Analysts are stumped, until the knot is untangled by one particularly bright young woman at the Office of Naval Intelligence--Katie Ryan, the youngest daughter of President Jack Ryan. Like her father, she sees patterns where other don't, and she's determined that the Russians are about to launch a super missile submarine, the Belgorod. 

Now the race is on to determine where the sub is and whether it poses a threat to the continental US.