Three thousand years ago, the Deep appeared without warning. This alien life form was quickly put to service teleporting people and cargo across great distances, which allowed mass colonization throughout the galaxy. It has also allowed Lancaster, the organization which controls access to the Deep, to grow wealthy and powerful. Cross Lancaster, and you are forced to travel between planets using standard faster-than-light technologies. Nobody wants that!

Tembi Stoneskin is having a very bad day. A Witch in service to the Deep, she spends her time disarming bombs in shipping stations. On her way home to Lancaster, the Deep shows her the aftermath of a weapons test powerful enough to slice a moon in half. While the Deep is a vast intelligence, it is a terrible communicator, and relies on its Witches to translate humanity’s requests into thoughts, moods, and impulses that it can understand. Tembi is a young Witch, but she is a skilled translator and she has learned how to speak with her powerful alien friend.

As they set off to find the source of the weapons test, Tembi and the Deep are pulled into the ongoing war between Earth-normal humans and genetically modified humans. But all wars are founded on excuses, and the Blackwing army has much more to hide than a simple shattered moon.