Achilles' Heel (Paperback: 470 pages)

The Barents Sea, Russia's graveyard for nuclear reactors, is where a Romeo class diesel-electric submarine is supposed to be scuttled. After a mysterious explosion, the sub disappears without a trace and the ship and its crew are presumed lost. Bill Lane suspects that the Russian sub hasn't sunk, and follows a trail of sub-sea anomalies to the coast of Morocco. There he discovers that Yermin has masterminded the theft of the sub to use it as a bargaining chip on the black market.

Yermin has captured Lieutenant Commander Francis Shipley of the British Intelligent Service, planning to use her relationship with Lane against him -- and he may have finally discovered Bill Lane's Achilles' heel.