Without warning or provocation, an alien weapon appears above Earth and unleashes a blast that kills millions across two continents. A second such weapon could destroy the entire planet. In a desperate bid to save Earth and its people, Starfleet must change its mission from one of peaceful exploration to one of military service.

In this Star Trek: Enterprise adventure by Michael A. Martin and Andy Mangels, only the starship Enterprise is fast enough to stop the production of a second Xindi weapon. But the crew cannot do it alone, and Captain Jonathan Archer accepts a contingent of Military Assault Command Operations personnel - battle-hardened soldiers known as MACOs - on board his ship. These two very different services share the ship and work together - or else.