Central to the story, which is filmed impressively in black and white (the director was also the cinematographer) with all the realistic advantages the style communicates, is Yalitza Aparicio in the role as the dedicated Cleo. Remarkably, given her deeply sympathetic performance, Aparicio is not a professional actress. Cleo looks after a family, consisting of Sofia, the mother (Marina de Tavira), four children (three boys and a girl) and their grandmother. We briefly meet the unfaithful father, who goes off on a business trip with another activity in mind. There is also the important family cook, Adela (Nancy Garcia), who is very close to Cleo in friendship as well is in work.

There is special poignancy in Cleo’s relationship with the children, who are a handful, and one harrowing scene at the beach emphasizes how much Cleo cares for them. She works for modest wages, but when she gets into trouble, help is provided.

The trouble arrives when she finds herself pregnant after an encounter with a lout who refuses to have anything to do with her when she confronts him and says it is his child. Aparicio’s understated performance is what holds the film together even though we also become involved in the other characters.

Cuarón makes a point of stressing life in Mexico City, starkly dramatized by including shots of a major controversial event, a protest demonstration by students brutally confronted by rampaging police—an episode in 1971 called the Corpus Christi Massacre. The director handles this by showing what is happening from the viewpoint of Cleo and the grandmother who observe the demonstration and the police attack.