For the first five books of the Frontlines series humanity was pushed from their many homes amongst the stars back towards Earth. The aliens known as Lankies eventually set up a foothold on Mars and began to batter Earth and put humanity on the brink; however, in the last book we saw the human forces finally push back. Although the Lankies are still on Mars it is no longer a launching point for their military and human forces control the orbital. This book starts a number of years later over the last few years there has not been a single Lankey attack launched against Earth so of course it is time to get curious and figure out what is going on. What better way to do that than to head back out of our solar system and see what the Lankies are up to elsewhere. What could possibly go wrong?