Infestation (Unseen Things, #15) / Unseen Things (ePub)

The akkelet started out as yet another zeth genetics experiment, but they quickly turned into something that even the zeths were deathly afraid of. When they escaped to another world and continued to breed exponentially, the zeths were left with no choice but to devote an inordinate amount of their military resources to wiping the akkelet out of existence. Unfortunately, before they had a chance to launch their attack, the nathalis blew up their moons and destroyed all seven of the zeth worlds. It seemed like the right move at the time, as the zeths had developed a nasty bioweapon that they were readying to use against them, but in doing so, they stopped the zeths from destroying a threat that would eventually find its way to all four of their own worlds.

Not only are the akkelet able to reproduce both rapidly and prolifically, but they're telepathically connected through an intensely powerful hive mind, and since the zeths created them as an experiment using version one of the serum, their hive mind operates at a frequency that blasts through the minds of anyone who's had the serum, thereby negating their ability to use any of their mental abilities. As the invasion begins on the nathalis worlds, their friends from the Human and Blue Fin dimensions must put boots on the ground alongside the nathalis military in order to fend off the threat. Unfortunately, the akkelet are advancing so single-mindedly, and in such massive numbers, that their only hope lies in Andrew and Naelen's attempt to acquire a frequency jammer that's capable of canceling out the hive mind, so that those on the ground will be able to use their mental abilities to eliminate the threat. The question is, will they acquire the technology in time to stop the invasion, or will their ground forces be overrun before they can return?

Also, when Derek, Jarrod, and Logan pry Charles and Richard out of the lab to go on a little trip to the planet Gliese 667 Cc, they end up finding a crashed ship and a dead bridge crew from a parallel dimension that leads them to uncover a tale of revenge against a massive and corrupt corporation that operates as their world government in exchange for free energy.

Finally, Darla and Logan's relationship has reached the point where he's ready to bring her into the family. Unfortunately, there's a member of her own family who's been missing for many years. Her father disappeared while on a trip to Texas to visit a friend, and no trace had ever been found of him. When Logan asks Derek to see if he can locate him, the search leads him somewhere he never expected, and leaves them with a lot more questions than answers about how he got there.

Infestation is book 15 of the Unseen Things series.