Harm, Mac, and Bud observe war games in the Black Sea, Mac aboard a US ship, Harm and Bud aboard a Russian ship. The two skippers, old enemies, try hard to settle grudges; the Russian, a psychotic, goes too far. Harm and Bud reach safety.

Harm finds his father's trail in Siberia; he and Mac (who speaks the language) go to Russia. Two Russian acquaintances intercept them. With help Harm and Mac "borrow" a MiG-29 (a copy of the F-14 Tomcat), but opposition suddenly appears.

Harm goes to Russia to help in reforming Russian military law; however, complications arise. Mac and Bud prosecute a Naval officer for espionage, then she too goes to Moscow. Harriet gets a small surprise, and Harm gets a large one.

Harm is distraught when his newly discovered half-brother, Sergei, is framed for a crime punishable by death, while Mac arrives in Russia to prevent a presidential assassination.

Bud feels anger and agony over the recent tragedy in his family; he considers courses of action and makes a decision. Mac moves a ring, and Mic prepares to return to Oz. Webb twice gives Harm news. A secret about Harriet comes to light.

A Russian nuclear submarine sinks while submerged with a US nuclear submarine nearby. The Russian government learns that the fault for the sinking lies with the Russians, but the officials seek to blame the US anyway. The US submarine leaders know what took place, but they feel reluctant to reveal that, because to do so would disclose an important advantage. After two surprising twists Mac takes a ride aboard a US submarine, and Harm takes one aboard a Russian submarine. The two boats wind up near each other, because the US vessel shadows the Russian one. An extremely dangerous situation develops aboard the Russian boat, and Mac and Harm take part in resolving the problem. Meanwhile a woman ensign in the US Navy graduates with honors in nuclear engineering from a college and from the Naval Nuclear-power School; she then applies but is rejected to attend the Naval Submarine School and to serve aboard a submarine; Mac and Bud advise her.

A Navy judge stands accused of vehicular homicide. Mac and Sturgis prosecute; Harm defends. Harm discovers the real cause of the wreck. Webb continues to pursue a terrorist, and Loren continues to promote trouble between Bud and Harriet.