While trying out the spy glasses, spy hat, and other items in their new spy kit, seven-year-old Henry and his dog Mudge make a new friend and form a spy club.

She used to work for the United States 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 person she trusted, but something she knows still poses a threat. When her...