'Hugo Duchamp Investigates: The second trilogy' contains the fourth, fifth, and sixth books in the series following Hugo Duchamp, a Frenchman living and working as a policeman in London who is about to have his world turned upside down.

'L'hombre de L'isle' (The Shadow from the Island) picks up after the shocking conclusion of Hugo's last investigation and the action switches to Ireland where Hugo races against time to solve the brutal murder of a priest in his most personal investigation yet which will leave him questioning everything he thought he knew and believed in.

In 'L'assassiner de Sebastian Dubois' (The Murder of Sebastian Dubois) Hugo's two worlds collide. His new life in Montgenoux is affected by an investigation from his past and he finds himself having to deal with a past he thought he had left behind and a pair of criminals who are determined to wreak their revenge on him. As he attends a crime scene at the newly opened Montgenoux prison, Hugo and Dr. Chapeau find themselves taken hostage and face a deadly race against time to escape their grasp of violent criminals with only one thing on their minds, Hugo's death.
The discovery of a thirty-year-old skeleton buried under the Beaupain vineyard in Montgenoux ('L'impondérable') triggers a horrific series of events in the modern day resulting in the murder of a prominent citizen and a murder/suicide. It all seems like an open-and-shut case. Hugo faces a complex web of lies and crimes dating back to the eighties which have devastating effects on Hugo and those he has come to love.