The Fifth Profession – David Morrell

When Savage and Akira meet, they are shocked to realize they both have vivid memories of seeing the other die in a past assignment, a shared history that is undeniably false. As they join forces with Rachel and evade pursuit by unknown adversaries, they work to solve the mystery of their jumbled memories, a phenomenon Savage identifies as jamais vu. Their investigation points to a conspiracy involving experimental brain surgery, hypnosis, and the CIA, ultimately leading them to Japan to confront a truth that could shatter their reality.