What is the theme in Deep Six by Clive Cussler?

The theme of justice comes into this novel in several different ways. The first is Pitt's outrage at the death of Julie Mendoza. Mendoza dies on board the Pilottown when an earthquake causes her to fall and break her legs, the fracture tearing her safety suit and exposing her to the nerve agent on board. Pitt has not known Mendoza for long, but found her interesting and is outraged that she would have to die such a painful death. Pitt becomes a bulldog as he investigates the ship and attempts to find out where the nerve agent came from. Unknown to him, the investigation will lead Pitt into an investigation of international intrigue and place his on-again, off-again lover in danger.