 Several years after the end of the Great War (detailed in the main Babylon 5 TV series) the former servants of the now-exiled Shadows attempt to avenge their old masters by introducing a powerful biological weapon into Earth s atmosphere. After five years of adapting itself to humanity s genetic makeup, it will kill every human being on the planet. Since this plague was the product of a technology far ahead of humanity s, there isn t enough time to develop an original solution - instead, humanity will have to comb through the ruins of older alien civilizations with the hope of finding some ancient, advanced technology that can cure the disease. Leading this high-stakes archeological mission is a starship of the new Interstellar Alliance, the Excalibur, and its crew drawn from the Alliance s elite troubleshooting corps, the Rangers.