Widely acclaimed for The Case of Doctor Sachs, centered on a provincial French physician, Martin Winckler now turns his hand to a remarkable crime novel set in Montreal. The Invisibles takes Dr. Lhombre from France to Canada, where he becomes involved with murder, violence, and a unique view of the province of Quebec and its indigenous tribes.

Doctor Charly Lhombre needs a change from his medical practice in a small French town, so when he is offered a sabbatical position in the Center of Ethical Research at the University of Montreal, he quickly accepts. He arrives at the Center to finds a thriving environment generously funded by its wealthy patron, Oscar Lachance. Everyone is delighted to welcome the doctor, and his colleagues are eager to explain to him the work of the Center and the power struggles and romantic entanglements within the team. They cannot, however, explain some strange events that have been happening in a shelter run by the University for Cree Indians living in the city.

Dr. Lhombre's plans for a quiet sabbatical go awry with a string of violent events: three defenseless, homeless Cree are attacked, and someone breaks into Oscar Lachance's apartment and tries to kill him. While Dr. Lhombre looks into the Center's difficult past, he thinks he sees a link between these events and a death that took place three years earlier—the murder of Kathleen Cheechoo, a beautiful Cree doctor and Lachance's life partner. Fortunately, Lhombre finds he has a surprising new friend, Rejane Lalumière, and is given a quick but thorough initiation into the Cree culture. Will that be enough to help Charly find the motive of the murders and stop the perpetrator?

The mystery, fascinating in its own right, is made even more interesting by the vivid portrayal of the Province of Quebec, the City of Montreal, and ethos of the Cree Indians.