The hero of Zodiac is Sangamon Taylor, aka S. T. As a leading member of GEE – the Group of Environmental Extremists—S. T. has spent years waging guerilla warfare against the forces responsible for undermining the ecology of the Eastern seaboard. When he learns that a large number of lobsters pulled from Boston Harbor have exhibited alarming levels of a carcinogenic substance called PCB, S. T., along with a band of like-minded cohorts, begins to investigate. Following a toxic trail that encompasses corporate malfeasance, genetic engineering, and presidential politics, he uncovers a conspiracy.