What is the main conflict in Deep Six by Clive Cussler?

Deep Six is a Dirk Pitt novel by Clive Cussler. Dirk Pitt investigates the Pilottown, a ship found on Augustine Island in Alaska with a nerve agent in her cargo hold. During what seems like a routine investigation, an EPA agent is killed. Pitt is outraged by this needless death and becomes determined to find the source of the stolen nerve agent in order to get justice for the EPA agent's death. Pitt is a bulldog, determined even when his boss needs him to focus on other investigations.