It’s apparent from the outset of new Netflix action flick Sweet Girl that this is a film that takes itself very seriously indeed. Within the first few minutes, we’re treated to an incredibly portentous voiceover, the first stirrings of a rather overbearing score, and a slowed-down, sombre rendition of Sweet Child O’ Mine. Whatever else, it’s not an opening that gives the impression this is going to be a laugh-a-minute affair.

Directed by first-time feature filmmaker Brian Andrew Mendoza, this rather muddled film is ostensibly about Ray Cooper (Jason Momoa) and his daughter Rachel (Isabela Merced) as they embark on a quest to get revenge on the people they believe responsible for the death of Ray’s wife.

That list of wrongdoers is initially headed up by Simon Keeley (Justin Bartha), the CEO of the fictional BioPrime Pharmaceutical company, whose decision to pull a cheap and accessible drug from the market had eradicated any hope Ray’s wife had of making a recovery from her critical illness. An early – unintentionally funny – scene sees Ray confront Keeley as he appears on a television phone-in, telling him in an irate growl that he will hunt him down and murder him should his wife die. It’s one of many mortifyingly overwrought moments in a film full of them.

Anyway, all of this is essentially prologue, as following the untimely murder of a VICE journalist who tries to pass on vital BioPrime information to Ray, the action jumps forward two years, with Ray and Rachel kickstarting their vigilante mission in earnest. In the melee of events that follow, the BioPrime conspiracy becomes increasingly convoluted, a pair of FBI agents set out to catch Ray and Rachel, and a charismatic hitman emerges on their tail – as their mission looks increasingly impossible to complete.

To begin with, it’s all just a little dull. The plot moves forward fairly quickly – with several time jumps in the opening stages – but never really settles into any kind of rhythm, with the clumsy setup preventing any real momentum from gathering. Momoa is a brooding presence as Ray, but there isn’t any discernible chemistry between him and his supposed daughter, with their dynamic never coming across as particularly engaging or believable. You don’t get the impression that these characters are real, living people that exist outside the movie – which makes it that much more difficult to care a jot about what happens to them. Meanwhile, the dialogue is uninspired and often exposition-heavy, the action set-pieces are distinctly mediocre, and the pharmaceutical conspiracy plot is half-baked and not particularly interesting. Above all, it’s just not really any fun.

And then, about 80 minutes into the film, comes the twist. I won’t spoil the nature of the reveal in this review (go here to have the Sweet Girl ending explained), but suffice it to say that I was in two minds about whether to angrily turn off the television in protest or to laugh uproariously. For a start, the film hadn’t really earned such an outlandish rug pull, but to be honest I struggle to think of a movie that could have pulled it off – for the simple reason that it just doesn’t make much sense. The whole thing doesn’t hang together, and it’s particularly egregious given how seriously the film has taken itself up to that point – while it also makes it even more of a chore to then sit through the remaining 20 minutes or so of the runtime.

For a while, it seems that Sweet Girl will simply be an underwhelming and forgettable action thriller – and for the most part, it is those things – but the botched twist ensures it becomes something of a true disaster. Best give this one a miss.