In Morocco, sex outside marriage is punishable by up to 12 months in prison. But when unmarried Sofia gives birth, in this debut feature from Meryem Benm’Barek, her family’s biggest fear is not her going to jail, it’s preserving their honour. The film is straightforward, a blunt social-realist drama. (Sofia goes into labour at a kitchen sink, while washing up.) Only at the end does it dawn on you how carefully the story is plotted: something happens that recasts everything that has gone before – and, if anything, makes the story even more grim.

Maha Alemi stars as 20-year-old Sofia, who doesn’t know that she is pregnant until her waters break during a family party in Casablanca. It’s never clear whether Sofia, who didn’t gain much weight, was completely unaware of the pregnancy; perhaps she suspected it but had blocked it out. Her face is mostly blank, and she walks through the film numbed and zombie-like. After the birth, her family is disgusted – and terrified that a scandal will blow her dad’s business deal with wealthy entrepreneur named Ahmed. (Ahmed is played by Mohamed Bousbaa. Like a bit character in a murder mystery, watch him – he’ll be important later.)

Everyone agrees the only solution is to find the man who got Sofia pregnant and persuade him to recognise the baby. Sofia and her rich cousin Lena (Sarah Perles) drive around to find the guy, Omar (Hamza Khafif), who turns out to be no one’s idea of a perfect son-in-law.

Benm’Barek refuses to flatten her script into a simplistic tale of misogyny. This is about class, too. If you have the money and the connections, you can bypass the law. Things happen to Sofia that would never happen to middle-class, educated Lena. What a clear-eyed and pitiless film this is; it left me hankering for the chinks of tender optimism in a Ken Loach movie.

• Sofia is available on 23 April on Your Screen.