“The emotions you are having are not your own. They are someone else’s. You are not the cat – you are inside the cat.”

The third mesmerising, teeth-setting feature from writer-director Josephine Decker (Butter on the Latch, Thou Wast Mild and Lovely) opens with what could pass for a cod-Buddhist mantra as the film’s troubled teenage heroine (Helena Howard) purrs and picks her way into the dining room before flopping prone onto the furniture. Her mother (Miranda July) plays along by stroking the girl as cat. This is an acting exercise for Madeline’s experimental theatre group, a troupe overseen by the overbearing, plummy Evangeline (Molly Parker). Perhaps. Madeline’s Madeline consistently blurs the line between art and madness, reality and fantasy. An early encounter between Madeline and a flapping man with mental health issues sends her spinning wildly. Is this involuntary or performative?

Mental illness

Throughout there are dark hints of mental illness: a psych unit is mentioned and Madeline has a collection of what may be hospital bracelets. Decker and her cinematographer, Ashley Connor, simulate altered states with drifting, fragmented focus. Occasionally a cappella outbursts from Roomful of Teeth and compositions by Caroline Shaw on the soundtrack add to the film’s rising anxieties and uncertainties.

While their dinner table encounters can segue from playful to explosive, a mother-daughter dynamic that was expertly pinned by Greta Gerwig’s Ladybird, there’s an unease about Miranda July’s character that may go beyond frazzled mom. When the 19-year-old Madeline tells her mother about kissing a boy, the response is disproportionately overprotective: “Maybe we shouldn’t have rushed into something with so much responsibility; he could have herpes.” Mother has an odd rival in Evangeline, who coos over and cajoles Madeline into exploiting her homelife and vulnerabilities for the sake of character. “I dreamt you were my daughter,” she says silkily. Her subsequent actions are anything but maternal.

Formally fearless and endlessly intriguing, Madeline’s Madeline puts experimentation in the service of racketing tension. Writer-director Decker discovered Helena Howard while judging at a teen arts festival in 2014. All their stars must have been out. Veterans July and Parker are excellent but it’s Howard who puts in one of those rare, explosive turns that leaves you to consider the very nature of acting.