Joachim Jo Saint-Clair is a veteran detective in Paris elite Criminal Brigade tackling the city's most challenging murder cases.

A police commander in Paris is as brilliant as the psychopathic killers he tracks down. Crimes occur in the city's most iconic locations, such as Notre Dame or the Eiffel Tower. He gets assistance from an unorthodox nun who works in the city's most troubled areas. While attempting to solve the most mysterious crimes plaguing his famous city, he also struggles with personal issues, such as reconnecting with his estranged daughter.