"What would you say if your daughter told you her boyfriend pushed her down the stairs but it's okay because really it was just an accident?" Questions like this are at the heart of It Ends with Us, based on the bestselling novel of the same name by Colleen Hoover. This is a message picture about what it takes to break the vicious cycle of domestic violence. It is not subtle.

After the emotional turmoil of her estranged father's funeral in Maine, our heroine, the impeccably fashionable Lily Bloom (Blake Lively, the best clotheshorse movie star since Kay Francis), breaks into a rooftop to peer at the vast beauty of Boston's skyline. Before she can do much introspection, she meets the impossibly handsome and impossibly named Ryle Kincaid (Justin Baldoni, also the film's director), a neurosurgeon (naturally). Baldoni comes barreling into the scene like a hurricane, hurling a pair of steel chairs across the rooftop in anger. Instead of repulsion from this violent act, Lily finds herself intrigued and drawn to his charm and megawatt smile. Their playful patter, peppered with barbs veiled as flirtation from Ryle, ramps up until the dashing surgeon is summoned back to the hospital by his beeper.

This is of course, not the last we see of Ryle. Although Lily repeatedly insists that she just wants to be friends, Ryle pursues her, ignoring her many pleas just as flagrantly as she ignores all his red flags. Lust is a hell of a drug. Quickly, Ryle's negs and flirtatious barbs ramp up, transforming into toxic jealousy and other forms of obsessive behaviour. This includes inviting himself to dinner with her mother by dropping the L-word for the first time, one of several such instances of emotional manipulation he brandishes like a silver-tipped dagger. Before she knows it, Lily is not only in a relationship she didn't really want, she herself becomes an outlet for Ryle's raging temper.

The early scenes of Lily and Ryle's volatile courtship are interwoven with scenes in which teenage Lily (Isabela Ferrer) falls in love for the first time with a schoolmate named Atlas (Alex Neustaedter). The soulful boy is squatting in the abandoned house across the street from hers, fleeing his mother’s abusive boyfriend. The generous and non-judgmental Lily offers both, aid and friendship when Atlas needs it the most. He in turn offers her a caring shoulder and a safe place to finally express the fear she feels as she watches her father physically abuse her own mother over and over again.

These scenes are innocent and tender, the two young actors imbuing the teenagers with just the right balance of world weariness from the violence they’ve already endured and the irrepressible hope that comes with youth. Once Brandon Sklenar enters as the grown-up Atlas, he is able to craft an effortless, natural chemistry with Lively that is nearly as strong as these early moments, although they both are far too fleeting.

It Ends with Us is a fine-looking picture. Baldoni and cinematographer Barry Peterson know how to frame movie star faces in flattering medium close-ups, allowing every nuanced emotion, every twinkle in their eyes to transport the viewers on this emotional journey with them, even when the characters feel more like didactic cyphers than fully-realised human beings. Lily’s flower shop (which never seems to have any customers) is a Pinterest board brought to life.

Lively does her best to add emotional layers to Lily so we see her internal growth, but this process is often hampered by the film around her. The few women in Lily's life – her so-called best friend Allysa and her mother Jenny (Amy Morton) – are underdeveloped, relegated to a handful of scenes that largely exist as plot points. The PG-13 rating keeps the violence Ryle inflicts on Lily, or her father's violence in the flashbacks, to a minimum visually (and often seen in slow motion or in choppy montages), Christy Hall’s script unfortunately often falls into "as the father of daughters" territory, giving more care to explaining why these men are the way they are (especially in Ryle's case, in the film's most cringe-worthy twist) than it does to the psychology – let alone the economics – of why women often stay with abusive partners. Instead, this subject, which should really be the key to the whole story, is covered in one very short scene between Lily and her mother. The forced love triangle once Atlas re-enters Lily's adult life also restricts things, causing Lily's life to once again orbit mostly around the men in it.

It Ends with Us is certainly not a bad film. At times, it's actually quite good and its central message is crafted with intention and care. You just wish it had a sharper focus on Lily's interiority, her life beyond her trauma, and who she really is in relation to herself, and herself alone.