Here is a mysterious and opaque movie, a feature debut from 42-year-old Brazilian artist and film-maker Maya Da-Rin. It does not give up its meaning easily, or perhaps at all. Newcomer Regis Myrupu won the best actor prize at the Locarno film festival for his understated performance as Justino, a member of the indigenous Desana people working as a security guard at a container port in Manaus harbour in northern Brazil. He is a widower, fussed over by his affectionate daughter Vanessa (Rosa Peixoto), who has just got into medical school at Brasília and will have to move away very soon and may not see her dad for many years. And perhaps that is what has caused a strange, profound unease in Justino. He suffers from a fever which is resistant to diagnosis. He becomes dreamy and inattentive at work and is called to see the stern head of human resources, who after some perfunctory inquiries about his mental health gives him a warning.

But maybe his fever has a larger social or even cosmic origin. As an indigenous person, he is alienated from many in the city; a fellow security guard reveals himself to be bigoted towards “Indians”. The younger generation no longer hunt or fish the way Justino’s family once did; he jokingly says that his son has become enfeebled by eating supermarket food. But later, with a visible twinge, he will tell the doctor treating his fever that this is exactly what he himself eats. And the local community is disturbed by reports of a strange beast wandering about and killing animals. Could it be Justino’s restless spirit made flesh?

The Fever is a calm and quiet and subtle film, a little inert perhaps, but deeply engaged with the hidden lives of Brazil’s indigenous people. There is poetry in it.

• The Fever is released on 6 August in cinemas.