When called to do battle many light years from home, the first Marine Interstellar Expeditionary Unit rose to the challenge - and now thousands of enslaved humans have been freed from the alien yoke. But Earth is 21 years older than the home planet they originally left, and the Marines need time to retrain and readjust - time they do not have, due to the bizzare disappearance of a detachment of their brothers- and sisters-in-arms. It is a mystery, but there is a starting point: an ancient wormhole threading through the Sirius system. Whatever waits on the other side must be confronted, with stealth, with force, and without fear - be it an ancient enemy or a devastating new threat.
The Marines are heading into the perilous unknown...and what transpires there could reshape the universe for millennia to come.