Tres Navarre, book 3: The Last King of Texas
Rick Riordan2000

When a controversial English professor is found shot to death, Tres Navarre — P.I. and Ph.D. — is the only local academic crazy enough to accept the emergency opening at the University of Texas at San Antonio. Police assure him they already have a suspect, so while they wrap up the open-and-shut case, all Tres has to do is teach three classes, grade on a curve ... and walk in a dead man's shoes.

It should be an easy assignment — but one thing Tres doesn't do is easy. When the evidence in the case starts looking a little too perfect, when the killing doesn't stop, Tres takes on some extracurricular research into the heart of an assassin — and lands in a high-stakes game of gangster honor on the darkest streets of San Antonio's West Side....

Titre original : Tres Navarre, book 3: The Last King of Texas (2000)