She used to work for the U.S. government, but very few people ever knew that. An expert in her field, she was one of the darkest secrets of an agency so clandestine it doesn't even have a name. And when they decided she was a liability, they came for her without warning.

Now she rarely stays in the same place or uses the same name for long. They've killed the only other person she trusted, but something she knows still poses a threat. They...