It was questions like these that exercised the French director and screenwriter Fred Cavayé while developing the screenplay for Farewell, Mr Haffmann, set in Paris in 1941, during World War II. The Nazi occupation is a setting ripe for high crimes, duplicity, and more.

Farewell Mr Haffmann, the story of a Jewish jeweller who drew up a fictitious sales contract to place his home and business in the hands of his genial assistant, has been a popular outing at the recent French Film Festival and is now in release. My chat with the director, Fred Cavayé, on Zoom was relaxed and genial despite the early hour in France. Although he was apologising for not being quite awake, he was absolutely on point.

His film has connected with contemporary audiences here who are neither French nor were occupied during wartime. Is this because the film confronts us with subtle questions about morality, engaging our sense of personal ethics, while the story unfolds in another very different time and place?

"I did wonder if my autopsy of a person who falls into a bad situation, my autopsy of a bastard, was going to resonate outside the frontiers of France, but of course it would. It is a contemporary and universal dilemma."

After sending his wife and family to relative safety elsewhere in France, Joseph Haffmann (Daniel Auteuil in the role) initiates a deal with his trusted workshop assistant, Francois Mercier (Gilles Lellouche). He proposes to leave his home and business to Mercier, supported by a fictitious bill of sale, to retrieve all of the property when the war was over.

There's no contingency plan for what then ensues. Haffmann is unable to escape the city and has to return home almost immediately, requesting refuge. He then begins a new life hidden in the basement, also the workshop, as Mercier's invisible assistant. It is an ironic reversal of roles.

Of course, the film is asking us what we would do in the same situation as Mercier?

"Yes, effectively."

The screws really begin to turn when, as Mercier's employee, Haffman begins to recognise the precious items he is working on, refashioning them to the taste of the Nazi clientele, as the confiscated property of former Jewish clients. His former assistant, a gentle, good man of ordinary ambitions, has gone over to the dark side.

So, Mercier essentially becomes a collaborator.

"Not through questions of ideology. I was interested in someone who became a collaborator, not because of ideology, but through self-interest, through taking advantage in an everyday way, making the most of small opportunities offered for self-advancement. A very small monster, but nonetheless a monster."

And it's a deal with the devil.

"A Faustian bargain, yes. From the moment Mercier recognises the jewels of former clients and has a debate with himself about it, but opts to go ahead, that's the moment when it becomes Faustian.

"Collaboration is still a taboo subject here."

Accepting Haffmann's deal in the first instance is what one might expect of a character like Mercier, who dotes on his sweet wife Blanche (Sara Giraudeau), longs for children of his own, and has had to wear a leg brace because of polio.

If it was at first hard for Mercier to turn down Haffman's proposal, the new circumstances made a seemingly charitable act even more difficult. There were of course, severe penalties under the Nazi occupation for concealing Jewish people. However, Mercier's initial actions are followed by a downward slide.

The screenplay, co-written with Sarah Kaminsky, is adapted from the successful stage play of the same name by Jean-Philippe Daguerre.

How did Cavayé adapt it to the screen?

"The key change in the film was Francois becoming an evil character, wanting to inflict social revenge, wanting people to believe he had talent, and stealing from his master.

"It's the theft of a life. I wanted to tell the story of a man who so much wanted the life of another man, that he was prepared to cause his death."

Daniel Auteuil and Lellouche would be reason enough for many people to go and see this film, especially as their characters suddenly find their relationship completely upended by the German occupation and the persecution and deportation of French Jews.

The third fine performance in this weird kind of menage-a-trois is that of Sara Giraudeau as Blanche, Mercier's sweet wife.

It may be a revelation for those who don't already know her work as a scientist infiltrating an Iranian nuclear facility in the television series The Bureau, and as a country veterinarian with an aberrant farmer brother in Petit Paysan, also known as Bloody Milk.

How did Cavayé pull together his cast?

"I began with the character of Francois, starting with Lellouche who I knew well from having made four films with him.

"I knew he would just adore the role of someone who became a monster.

"I also knew I wanted one of the three top French actors, a [Gerard] Depardieu, an Auteuil, or a Lellouche, and to make it a real meeting of two stars.

"Then, there was the character of Blanche, who is a central character but this is only revealed bit by bit during the film.

"It interested me that Sara Giraudeau, who is young and doesn't yet have the career of the two male leads, has a kind of innocence, a child-like presence that transforms into a strong woman, as she becomes the true force of the film.

"I knew her work in Le Bureau and Petit Paysan, and it was the transformation from the child to strong woman that really appealed to me," Cavayé says.

Even at the end, I suggest, you don't think she will follow through, but she does.

"Francois and Blanche have different trajectories."

Cavayé crosses his arms in the air, forming the shape of an X.

"Francois is very empathetic to begin with and she starts off as a less engaging character, but their paths cross during the story and head in very different directions.

Is it a psycho-thriller?

Kind of, says the fan of American cinema whose filmography includes thrillers.

Is Farewell, Mr Haffmann a war film or a thriller?

"Ah, it's a war thriller. More a war thriller than a war film, where the Germans don't present any danger."

Great answer.

Farewell, Mr Haffmann is now in cinemas.