After a disastrous encounter with an alien species, Captain Roc Masters finds himself exiled on a rundown station in the asteroid belt, commanding an ancient starship with a near-mutinous crew.
Just as he finally resigns himself to his fate, the aliens return to attack Earth.
With the inner worlds crumbling and most of the Earth and Martian navies sidelined or destroyed, it's up to Roc and his lone starship to hold the line.