From the Product website:
A COBRA AMIDST VIPERS...
From within the heart of the insidious organization VIPER, a new evil has arisen... one that wishes to conquer both VIPER and Earth! Can your heroes survive the challenges to come and save humanity from the clutches of King Cobra and his minions of COIL?
In Chapter One, Showdown At Snake Gulch, the heroes receive word that all is not as it seems at a tourist attraction in New Mexico. Investigation uncovers a VIPER Nest where a fiendish plot has been put in place to cripple VIPER and launch a scheme of world conquest.
Clues gathered at Snake Gulch lead the heroes into Chapter Two, The Ophidian Plague, in which King Cobra unleashes a virus that turns people into serpent-men. As they struggle to contain the plague and keep the violent serpent-men from destroying the city, the PCs have to track down the villain who helped King Cobra defect from VIPER.
An encounter at the end of Chapter Two starts the events of In The Coils Of The Cobra. The heroes chase King Cobra’s minions through the sewers to the Hothouse, an underground jungle and King Cobra’s lair. There they must find and confront the master villain and his followers and recover the cure for the plague before he can escape!
Chapter Four contains complete details on King Cobra, his superpowered inner circle, and the agents of COIL — an all-new master villain and criminal organization!
Uses characters from Champions Universe and Conquerors, Killers, And Crooks. The VIPER sourcebook is helpful, but not necessary.