From back of the book:
The Venusian Apocalypse
Venus: the jewel in the crown of Bauhaus, site of their greatest cities and most productive factories. Home to two Cathedrals, and millions of staunch Brotherhood supporters. Venus is a bastion for the Brotherhood on the face of the evil of the Dark Legion. Yet might Venus stands as one of the largest and least explored of the colonized planets and hidden within its deep jungles are secrets that could undo all mankind. When the greatest of all evils escapes its bonds to wreak havoc there can be only one result: the final destruction of Venus and maybe the whole system. Unless of course someone can stop it first.
The Four Riders
Heimburg quakes in the wake of the Battle of the Second Seal. A lone Capital Officer plots the downfall of all humanity, starting with the city that is Bauhaus' pride and joy. The players becomes dupes in a scheme to release the deadliest plague mankind has ever known, a disease that could wipe out life on Venus in a matter of weeks. Framed for a crime they did not commit, our heroes must fight to prove their innocence and hopefully save the world from a madman's scheme for bringing an end to humanity's hold on the second planet from the sun.