There’s an enjoyably inscrutable performance at the heart of this Brazilian fairytale for grownups. Clara (Isabél Zuaa), an unsmiling mystery women, arrives at the luxurious São Paulo apartment of pregnant Ana (Marjorie Estiano), to be interviewed for the position of nanny. But is that really the role on offer? And is Clara an entirely honest applicant?

The first third of this two-hour-plus film keeps us wondering. It’s clear that something is off between the women, but impossible to determine where the balance of power lies. Is this a Rosemary’s Baby-style horror about satanic foetus worship? A Parasite-like study of the subversive intimacy between domestic servant and employer? Or some unholy combination of the two? Then, with all the sprightly mischief of one of Ana’s country-music workout videos, the plot dances off again, in an entirely different direction.

To say any more would be to ruin the unpredictable pleasures of a genuinely surprising film, but everything Good Manners does – from lesbian sex scenes to furry animatronics – it does with elegance, humour and in shades of moonlit blue. Rui Poças’s painterly cinematography turns the tower blocks of a modern city into a kind of enchanted wood, complete with its own take on the big bad wolf from the storybooks.

Clara proves as hard to ruffle as she is to read, a quality that is sorely tested by the film’s events. Some may appreciate a strand of body horror that relates specifically to the female body and motherhood. More squeamish viewers can be reassured that these grisly moments are rare and interspersed with musical numbers. Also contained within the story is a heartwarming and timely tribute to care workers, both unpaid and underpaid. This satisfyingly strange film really has it all.

• Good Manners is available on Mubi.