A strange tale of cause, effect and revenge, with so many moods and tones it's self-described as 'action war black comedy-drama'. There's only really one genre not represented because the characters never break into song.

A young lady in Eastern Europe shopping with her elderly grandfather considers a bike for her Christmas present, but decides she wants one of another colour instead. After they leave the shopkeeper organises a gang of petty thieves to steal one of the right colour, hoping to make the sale.

The stolen bike belongs to Mathilde (Andrea Heick Gadeberg), who then has to be driven to school by her mother Emma. They then realise the car won't start, prompting a trip by train. Emma talks to her husband, Markus (Mads Mikkelsen), a stoic senior Danish army officer stationed in the Middle East. He's standoffish and curt with his wife, disappointing the family by telling her he's been asked to stay another few months and has accepted, something he apparently does and which disappoints them often.

Meanwhile two academics, Otto (Nikolaj Lie Kaas) and Lennert (Lars Brygmann) are presenting an algorithm they claim can predict future events given enough data, but their employers are less than impressed and let them go. Downtrodden, Otto gets on the same train Mathilde and her mother are on, and soon after he notices a tattooed man behaving strangely and getting off the train another train hits theirs, killing dozens including Emma and injuring countless others.

Markus comes home to his bereaved daughter but it's clear he's a terrible father, more or less telling her to toughen up and get over it, proving no support to the distraught girl. Meanwhile Otto approaches Markus, telling them he's convinced the accident was premeditated in order to take out a key witness set to testify against a fearsome bikie gang called the Riders of Justice.

Markus is hesitant but they bring in their hacker friend to try and use facial recognition to identify the man who got off the train, who they believe they find. When the foursome go to the goon's house and he pulls a gun on them, the three friends are shocked when Markus brutally disarms and kills the man. They realise they're slightly in over their heads but Markus now insists the Riders of Justice caused the crash that killed his wife and he wants vengeance.

From there at least four stories at once are going on. There's the story of the two scientists and their overweight hacker friend, a reference to classic Three Stooges-style antics. One of them even poses as a therapist and gets Mathilde to open up to him, declaring prognoses to her trauma that are as obvious as they are ridiculous, and we're left with a teenage girl's grief at the death of her mother that had been treated like serous drama suddenly fodder for broad comedy.

The soft spoken Otto has his own desire to see justice done which causes him to bond with Mathilde too, and she finds an erstwhile family in her father's strange new friends while he's unable to give her the love and support she needs, all without any idea they're really in her house to track criminals and plan killings.

And Markus, without even breaking a sweat, bursts into one enemy stronghold after another, blowing the bad guys away with gleeful action movie abandon that leads to the climactic stand-off at his house with everybody now in danger as hordes of bikers with automatic weapons close in.

The script, based on an idea by director Anders Thomas Jensen, is okay enough in servicing the story and there are as many affecting moments as there are funny ones. What's more skilful though is the way Jensen manages to shift gears without the movie slowing down or lurching awkwardly sideways. Just when you think you know what it is – from a tragic drama to a slapstick comedy – it turns into something else without losing any cohesion in the characters. Despite itself it all gels and you'll have a good time.