The Crossing by Michael Connelly

Harry Bosch has retired and he doesn't like it.  He was forced out and has a lawsuit against the force and he is at loose ends without the career he has been dedicated to.  When his half-brother, Mickey Haller, asks him to look into the claims of a client that he is innocent, Bosch's first response is an emphatic no.  He and his fellow detectives regarded those in law enforcement that became defense investigators after retirement as traitors; that they had crossed the line.

But the more Bosch hears about the case, the harder it is for him to refuse his help.  A man is sitting in jail, charged with the brutal rape and murder of a Los  Angeles city worker who was married to a sheriff's deputy.  The man in jail had a record from his youth when he was in a gang, but that was years ago.  He is now an artist and claims he was in his studio working when the murder occurred.  What finally sways Bosch to look into those claims is the realization that if the charge was false that it meant the real killer was free and walking around, maybe to commit more crimes.

As Bosch looks into the case, it doesn't take long before he stirs up interest in the minds of his former co-workers.  As he expected, he is regarded as a turncoat.  As he digs in further, he begins to undercover a plot that will expose corruption unheard of and a series of related crimes that no one else has thought to put together.  None of that makes him any more popular.

This is the eighteenth novel in the Harry Bosch series.   Those who like the series will be interested to see how Harry reacts to retirement and to being at loose ends.  It is interesting to see how his instinct for when something doesn't seem right leads him to one of the biggest cases in his career.  This book is recommended for mystery readers.