In the aftermath of a vicious sea battle with the Chinese fleet that ends in a nuclear blast, the presidential project submarine Silversides is dispatched on a search-and-destroy mission against the resurrected submarine Panther, recently converted by the Iranians to fire hypersonic electrical grid-killer missiles at the U.S. East Coast.

Anthony Pacino, the Silversides' chief engineer, is forced to abandon his mourning the loss of the love of his life and driven to fight to the death for his country, the mission and the crew. Returning also are the rich characters of the Silversides and former admiral and current Vice President Michael Pacino in this epic tale of undersea warfare.