Luke Lorentzen’s documentary has a fascinating story to tell about the peculiar state of health care in Mexico City. It seems that fewer than 45 public ambulances (can this really be so?) serve a population of some nine million. As a result, an industry has grown up around medical practitioners providing emergency private care on an informal basis. Midnight Family generates much interest by teasing us through the bizarre mechanics of the process.

The Ochoa family — all impressive in their different ways — are not, it seems, responding to contracted clients of heath insurance plans. Their ambulance turns up at medical emergencies and, after caring for patients, they begin the process of negotiating fees. Sometimes they end up with nothing. Sometimes they successfully deliver comforted victims to private hospitals.

This summary suggests the sort of Dickensian trickery we recently enjoyed in Parasite. That is not at all how the Ochoa clan come across. They are, for the most part, caring, responsible and well equipped. Lorentzen’s exciting film leaves us with the impression that, in such a hostile environment, patients may well have ended up in the best hands (worse operations would surely have not invited a documentary crew onboard). Fer and Juan Ochoa, father and son, are living life on a perilous ledge.

The shortish feature is packed with tense moments and disturbing shots that, without compromising the clients’ privacy, hint at the unhappiness just offscreen. A hand reaches up from the bottom of the screen and reveals a trail of blood. We see just enough of a rescued baby to know that she is not in great danger.

For all its sociological insights, Midnight Family does, however, feel just the tiniest bit thin around the edges. Audiences from outside Mexico will be left asking questions about the legal intricacies of this peculiar operation. The film comprises arresting episodes that fail to form a pleasing shape. Then again, that’s what life in a hurtling metropolis is like.

Opens on February 21st