Bulletproof Jack: Hunting Lee Child’s Jack Reacher by Diane Capri

Reacher sent a messenger. They stopped him with two bullets.

An unidentified man breaches all security and is executed by a skilled assassin on FBI Special Agent Kim Otto‘s doorstep. In his pockets she finds an advanced encrypted cell phone. Nothing else.
Kim arranges to extract the body and removes it to a private morgue for secret autopsy. None of the man’s biometrics match the databases. His identity remains concealed.
With nothing else to go on, questions multiply. Kim absolutely needs to know.
Who was this guy? Why was he trying to reach her? Who killed to stop him? What will they do next?
As the bodies pile up, Kim’s search leads her to Jack Reacher’s former lover in Lee Child’s Make Me. Michelle Chang knows Reacher well enough to be reliable, but Chang’s explanations are cryptic. When Kim presses harder for intel, Chang bolts.

The deadly investigation leads Kim from Detroit to Canada’s treacherous Niagara Falls region where expert killers and powerful government agents are not bulletproof—but Jack Reacher is.