“The Innocents” picks up a year after Quinn lost his re-election as sheriff. He then returned to Afghanistan as a civilian helping train the local police force. Now back in Jericho, Quinn is adrift, trying to figure out what is going on with his girlfriend who may not be getting a divorce, and contending with his estranged father, who has grandiose ideas about developing land adjacent to Quinn’s farm. His nemesis, the corrupt businessman Johnny Stagg, is in federal prison, but even more ruthless criminals may have moved in. The horrific death of teenager Milly Jones pulls Quinn back into law enforcement when his help is needed by Sheriff Lillie Virgil. Milly had been a popular cheerleader, but this year after high school graduation has been rife with family problems. Her latest job was working as a stripper. Milly’s death uncaps a swath of racism and fear as many suspects try to place the blame on others. Quinn’s friendship with Lillie and his love for his family are foremost, with his need for justice for Jericho and its people a close second. Yet Atkins allows Quinn to make mistakes and have foibles, making him an even more complex character. “The Innocents” moves at a brisk pace through Mississippi backroads to diners and cigar bars where deals are made but not always carried out. Atkins, who is continuing the late Robert B. Parker’s Spenser series, delivers another rousing thriller.