Recovering from his Operation Arctic Sting injuries, USS Teuthis Executive Officer Mac McDowell is tasked with laying SOSUS arrays in the southern Atlantic and off Thurston Island, Western Antarctica. Teuthis tangles with Argentine subs in the south Atlantic, then confronts a ChiCom sub off Thurston Island. Mac and his team experience serious setbacks at the hands of the ChiComs while installing a relay transmitter on a nearby mountain peak. Teuthis discovers an underwater oil operation off Thurston Island and is tasked with escorting a Taiwanese sub and underwater tanker under the cover of the largest military marine exercise since World War II: PacEx89. Teuthis is attacked by a Chinese Han-class sub and a previously unknown North Korean AIP sub despite the protection provided by three U.S. fast-attack subs. Will Mac and Teuthis complete their mission, or will they finally meet their watery graves on the Pacific Ocean abyssal plain?