Doppelganger

The continuation of the popular sci-fi action series

Geary and the crew of the Dauntless have managed to safely escort the alien representatives to Earth. But just before returning home to the Alliance, two of Geary's officers disappear. While searching for them, Geary ends up in the one place in the universe forbidden to all humans: the moon Europa. Any ship that lands there must never leave… or it will be destroyed. Geary faces a great dilemma – leave his subordinates to certain death, or risk the extinction of the human race?
He also has no idea that more trouble awaits him back home. Besides internal problems and Syndicate intrigues, the Alliance is threatened by a new, mysterious, and powerful enemy. No one knows who the Black Fleet belongs to, but with their superior firepower and tactical abilities, they could easily bring the Alliance to its knees.