In 1950s New York City, Lionel Essrog, a private detective living with Tourette syndrome, works for a small agency. His mentor and only friend, Frank Minna, takes on a case that seems enigmatic and consequently gets involved with dangerous individuals. When Frank is fatally wounded, he utters a few obscure last words that become the only clues Lionel has. Driven by a personal sense of duty and affection for his mentor, Lionel embarks on a quest to unravel the mystery behind Frank's death, using his unique observational skills and unorthodox approach to sleuthing despite his condition.

Lionel's investigation leads him into the complex web of Harlem's jazz clubs, Brooklyn's slums, and, ultimately, to the city's power brokers, exposing the depths of corruption and civic disenfranchisement. He encounters a diverse cast of characters, from brutal thugs to an enigmatic and passionate activist, Laura Rose, who is fighting against racial injustice and the destructive redevelopment plans of a ruthless tycoon who aims to reshape the city without regard for its poorer inhabitants. As he delves deeper, Lionel discovers that the case is much bigger than he ever imagined, touching on profound societal issues that are still relevant today.