Shirin (Akhavan) wants to take her breakup with Maxine (Henderson) in stride, renting a room in a hipster Brooklyn loft and seeking support from best friend Crystal (Feiffer) and her Iranian parents (Duong and Majd), who prefer to ignore her bisexuality. And Shirin's brother (Moayed) would rather she not force the issue before he marries his fiancee (Cotsonas). But the unemployed Shirin has no plan at all. While struggling to get Maxine out of her mind (and heart), she takes a job from a stoner friend (Adsit) to teach filmmaking after-school to 5-year-olds.

The film is a slice of life, essentially plotless as it meanders through Shirin's world. But there's a strong narrative in the structure of flashbacks, which fill in key elements that feed in to the present-day, including the entire history of her relationship with Maxine, who pressured her to come out to her family. Akhaven doesn't really have a burgeoning message to preach here, aside from knowing commentary about everyday ups and downs, self-awareness and the importance of facing the truth with a joke at the ready.

There are several classic moments along the way, including a brilliantly awkward threesome, some amusingly creepy new flatmates (who we'd like to see more of), and a strikingly realistic break-up argument. Yes, the film is a bit episodic, with clearly autobiographical touches that make everything unnervingly truthful. Sometimes it feels like Akhaven takes a goofy, comical approach when something more sharp-edged might be more effective, but it's so entertaining that we don't mind at all.

Her script is a constant barrage of dry humour: smart gags that seem to come from nowhere but slot seamlessly into Shirin's story. It's observant and honest, clever and often gut-wrenchingly funny. All of the characters are hilariously singular, endearing and infuriating in equal measure. But underlying the comedy is a real sense of yearning as Shirin struggles to forget what it felt like to be loved. Forgetting of course that she is still surrounded by people who love her.

It's been nearly seven years, but Amelia (Davis) still struggles with the death of her husband (Winspear), raising their high-maintenance son Samuel (Wiseman) on her own. And she's just about at the breaking point, as Samuel's obsession with monsters alienates his classmates, teachers and even family members like Amelia's sister Claire (McElhinney) and her daughter Ruby (Hurn). At wit's end due to sleep deprivation, Amelia asks the doctor to prescribe sedatives. So as Samuel becomes increasingly convinced that a monster called the Babadook (Purcell) has invaded their home, Amelia starts to believe it herself.

Writer-director Kent shoots the film like an old-school horror movie, using in-camera effects that ramp up the suspense. This isn't a digital menace: there's really something rattling and banging around the house, which is gothically decorated in greys and blacks (no wonder Amelia is so depressed!), complete with a locked basement where Amelia has stored her late husband's things. So with every Dook! Dook! Dook!, Samuel's eyes widen, Amelia's body stiffens and our hearts pound.

Both Davis and Wiseman give remarkably committed performances that explode with full-on emotion. This mother and son are so exhausted by their unresolved grief that they can barely cope in the real world. They take their frustration out on each other, and certainly don't have the inner fortitude to deal with something as menacing as the Babadook, which prowls and flutters, announcing its presence and intentions in a super-creepy pop-up book that only adds fuel to Samuel's raging nightmares.

Yes, what sets this film apart is the fact that it's much more than a scary monster movie. Even as the tension cranks up to nearly unbearable levels, the film is digging deeper into the characters, exposing their weaknesses as well as their strengths. A remarkable sense of steely determination underlines all of Amelia's worn-out terror, while Samuel's annoying caterwauling is accompanied by an eerily realistic surge of childhood yearning. This not only stirs the audience's emotions, but also makes what happens that much more frightening.

Jax (Marshall) works in social services with her best pal Bernie (Whyte), the only person she confides in about her unexpected pregnancy. She's understandably nervous about telling her husband Mark (Elba), because they've been through four miscarriages together. But their pre-teen son JJ (Lewis) figures it out. Meanwhile, JJ is hanging out with his school friend Lauryn (Frimpong), capturing a bird in the park and then trying to keep it alive. Eventually, Mark learns Jax's secret, and when he does the math he has a few questions.

The title offers a hint into Jax's perception of what happens: she thinks the baby was immaculately conceived. But then she also has visions of typhoons in the bathroom, so maybe she's not the most stable person in this family. To make matters worse, she refuses to say much more than a single syllable to anyone, so what's really going on is a mystery to the audience as well as everyone on screen.

Everything about this film is obtuse, from the pivotal conversations to a variety of random subplots and running jokes. Most scenes feel improvised with no rehearsal, which makes them feel realistic, including constant injections of comedy and intensity. And the minimalistic dialog leaves every scene open to a variety of interpretations. But all of this plays without any context. And since everything is so sketchy, it's impossible to engage with the story or characters.

That said, the cinematography and editing are excellent, and all of the actors deliver earthy, honest performances that let us see all kinds of things the script neglects to tell us. Marshall, Elba and the remarkable Lewis are each strong enough to hold the attention as the film meanders all over the place on its way to a rather cheap-gag ending. But in the moments of honest interaction the film finds some intriguing things to say about relationships.

Having escaped from servitude on a ship, Frank and Theo (Bransford and Regan) are living in a forest trying to steal the cash they need to sail to the America. But these woods are a notorious site for devil worship, and after some smoochy soft-porn sex they find it hard to sleep at night. Theo has both nightmares and waking visions of a gentleman (Mansfield) and an old friend (Campbell-Lewis) warning him: "Beware the devil man. He looks like a man but he's evil!" Further discoveries freak Theo out even further, but Frank remains sceptical.

Bransford and Regan are natural actors, although they struggle to improvise anything interesting to say to each other. The achingly simplistic dialog ("There's no place in the world for people like us!" "These things I've been seeing are real!) offers very little sense of who these guys are, and it's shot and edited in such a choppy, cheesy way that it feels amateurish. Much of the dramatic tension hinges on aching glances and musical cues, but there's only the vaguest whiff of a premise.

Writer-director Mansfield shoots this in a handheld style, using gimmicky edits and blurry imagery to try to obscure the microscopic budget. The demonic nightmares and flashbacks are both rendered in black and white, and there are constant glimpses of a gigantic phallic obelisk with no irony at all. All of this like it was shot with an iPhone on Hampstead Heath with costumes borrowed from an am-dram theatre company.

Even so, there's a vague sense of menace as these gay men fear for their lives, even if their relationship never resolves into anything resonant. And constant talk of malevolence means nothing when what we see is actually rather silly. So the only thing that holds our interest is the question of where this is headed, if anywhere. And while it's an intriguing demonstration of things an aspiring filmmaker can do with no money at all, it also proves that a properly developed idea is essential before you start shooting.