All the freshwater on Earth is gone. Now the alien invaders are working on the oceans and they are down to about half their volume. If humanity is going to fight back, then the time is now. In the last book, the Cheyenne Mountain biosphere team proved that their new weapon was capable of disabling the alien shields so they shared that technology with the Ghosts of Atlantis, the last remaining military submarine. Now they have discovered a potential new alien vulnerability which could allow an attack to disable all of the aliens planet-wide. They shared this knowledge with the GoA as well and Captain Noble has decided it is worth the risk to launch such an attack. While his team works on a longer range version of the weapon to make this possible Noble notices that biosphere goes dark. He must now decide between his attack plan and investigating what happened to the scientists who made it all possible - the scientists he promised to protect.
Things are tense as the few remaining humans try to leverage the only sliver of hope they have and it isn't clear if this series is going to have a happy ending. Although I still have issues with the plot point that fleeing to Mars makes any sense at all, author Nicholas Sansbury Smith continues to make his case as to why it does. This book doesn't conclude the story, which happens in book 4, Exodus, where Smith teams up with Anthony Melchiorri on the finale.
The audiobook version is narrated by Bronson Pinchot, who does a great job, and Audible has a boxed set of the first 3 books available, which is a good deal. Of course this means you are left with buying book 4 as well if you actually want to complete the series, but at least it is better than buying all 4 books solo.