Based on the award-winning 2011 book “Le quai de Ouistreham” by Florence Aubenas, “Between Two Worlds” explores the gap between modern-day France’s image of itself and the harsh reality of life among poor working-class people, many of them bereft, single mothers. Directed by Emmanuel Carrere (“La moustache”) and co-adapted by him and Helene Devynck, “Between Two Worlds” features the great Juliette Binoche as Marianne Winkler, a well-to-do writer who goes undercover among the women and young male immigrants forced by circumstance to take minimum-wage jobs cleaning toilets and changing linen on a ferry boat in the port town of Ouistreham in Normandy.

The workers are given minutes to clean each one of hundreds of rooms aboard a ferry bound for England. Their work begins before sunrise and must be completed before the passengers arrive. Many of the workers have no cars (or homes) and must get to the port on foot. Marianne wants to experience their lives from the inside. She is soon accepted. She makes friends with the easily frazzled Marilou (Lea Carne), who is little more than a girl, and Chrystele (a fierce turn by Helene Lambert), a not-so young single mother with three sons. Chrystele’s anger seethes just beneath the surface.

Marianne presents herself as an estranged wife with no work experience, who is in need of a job to subsist. She attends a job fair, where a low-level, civil service type encourages her to sell herself as a “cleaning technician.” Like her cohorts, Marianne is required to attend demeaning classes.

Marianne and Marilou are derided by bullying superiors for not working fast enough. Soon, it becomes clear that this sort of work in these kinds of conditions is a form of modern-day slavery. If Marianne and her fellow cleaners turn down a “shift,” they could lose their jobs. They have no protections that they are aware of. They and their families live paycheck to paycheck with nothing to buffer them from unexpected costs or inevitable emergencies.

Marianne must awake at 4:30am, even after a kind old couple lend her a car with which she ferries Marilou and Chrystele to work in the dark. On a trip back from a shift, Marianne and Chrystele stop at the beach, where Chrystele can afford to take her sons maybe once a year.

Even in such a living hell, there are subdivisions. Men don’t do bathrooms, Marianne is informed. “Between Two Worlds” reminds us that life for many is an infernal parade of toilets in need of cleaning. Is Marianne exploiting her co-workers for her own gain and acclaim as a writer? “Between Two Worlds” has moments evocative of Martin Ritt’s 1979 social drama “Norma Rae” with a great Sally Field. Like Field, Binoche’s gaze is so completely compassionate that we never suspect Marianne of exploitation. But we know that her coworkers will. Exploitation is their existential state.

(“Between Two Worlds” contains profanity and smoking French people)

Not Rated. In French with subtitles. At the Coolidge Corner. Grade: A-