The Guilty One by Bill Schweigart

A hero cop thwarts a brutal murder and can't remember a thing about it. But memories return—and so do the nightmares in this breathlessly paced thriller for fans of David Ricciardi and Michael Connelly.
Every town needs a hero—and Detective Cal Farrell fits the bill. He stopped an active shooter six months earlier, and now he's become the darling of the Alexandria press. The problem is that Cal remembers nothing from that day. He's working with a psychiatrist to recover his memories, but hasn't had much luck.
Then, on one of his morning runs, he is once again the first on scene for a grisly discovery—a body hanging impossibly high on a tree. Soon there's another victim, killed by a blade and dumped in a ravine. As the bodies begin to stack up, each staged more gruesomely than the last, Cal sees a baroque pattern to the crimes that no one else seems to understand—something out of legend.
As Alexandria dubs the...