Crank begins with a beautifully simple action movie premise: professional killer Chev Chelios (Jason Statham) learns that he has been poisoned, and only has an hour to live. But he finds that he can counteract the drug by raising his adrenaline level, and keeping heart pumping at full tilt.

It’s a recipe for non-stop mayhem as Chelios hunts down the men who did this to him, and the first half hour is a truly wild ride. Given that most people will be watching the film with some notion of the idea behind it all, the way he figures out the life-saving effect adrenaline has may seem a bit long-winded and clunky; but with everything else that’s going on in this short time–police chases, hold-ups, bar-fights–this is easily forgiven. Chelios has no time to plan an elaborate attack–he has to stay focused on where his next hit of energy is going to come from. The script handles this pace by sticking to a succession short, snappy, and mostly hilarious set-pieces. The editing is fast and jumpy, with lots of playful post-production effects.

Unfortunately, the middle part of the film flags a bit as Chelios picks up his girlfriend to try and explain everything to her. Although she is key to a few action sequences, she represents everything that Chelios wants, but can’t have, and that he must say farewell to. Her very presence is a dampener rather than a thrill. This also means that The Sex Scene (note the capitals) comes at a point in the film where the emotional tone has shifted more towards the serious and realistic.

The Sex Scene was clearly intended to be humorous. After learning that her boyfriend is a hired assassin rather than a computer games programmer, Eve (Amy Smart) storms out of the restaurant in Chinatown where they were eating. Chelios chases after her. Eve beats him off, he grabs on to her, and in the wrestling match that ensues they end up having fiery sex in front of a crowd of amused onlookers and a tour bus of Chinese school girls.

But at no point does anyone shout “rape” or try to intervene.

Given the complete lack of realism inherent in the rest of the film, and the blatant disregard shown for human life, perhaps I should have treated this scene with the same level of amused disbelief and detachment, but I couldn’t. It feels strange to say this about a film where I laughed at a gangster’s hand being chopped off and tossed around, but the Sex Scene felt inappropriate, and in poor taste.

It wasn’t the sex act itself, or the minimal nudity on display. It also wasn’t the way anger turned into sex; A History Of Violence has a far more shocking scene exploring the intersection of violence and lust, and it was not inappropriate. But elsewhere in Crank when Chelios pulls out a gun in the middle of a crowd or crashes a motorbike into a cafe, people run and cower in fear. The crowd reactions are correct in the context, and therefore remain inconspicuous compared to the action at the heart of the scene. In The Sex Scene, however, the reaction of the crowd is wrong, and therefore draws attention to itself. My suspension of disbelief was disrupted, and suddenly violence stopped being funny, and started being questionable.

I’m not going to condemn the whole film on the basis of a single mis-staged scene. But it sits right at the middle of an otherwise very good and cleverly constructed action flick, and it made me more critical of the remainder of the movie. It ends well, and appropriately, but it leaves behind most of the humour of the first half in a way that left me wondering whether its overall quality was down to luck or good judgement.