Relationships are such funny things. They either work or they don't. Not that they're ever that black and white. Sometimes they can be like pulling teeth or flogging a dead horse. Worst case scenario is they can be like pulling teeth from a dead horse. Very nasty business.

For Keira Knightley's latest role, she finds herself involved in a number of relationships, and sadly for Keira, none of them really work.

It's ten years after an awkward prom party and Megan (Knightly) is still trying to get her life into some kind of order at her prom reunion. Currently she's happy enough in her comfort zone. With no job prospects on the horizon, she helps her dad (Jeff Garlin) out by advertising his accounting firm on the side of a road twiddling and flipping a sign around.

Another thing that hasn't changed in the last ten years is her boyfriend; she's been dating Anthony (Mark Webber) since High School and they're still together. But things are likely to change on that front, when Anthony finally decides to propose.

Megan's feet get as cold as ice at the prospect. After helping a group of kids get beer, she befriends one of them – Annika (Chloë Grace Moretz) – and instead of going to a jobs seminar, she runs off to her place and hides.

During this time she meets Annika’s dad, Craig (Sam Rockwell), who at first isn't quite sure what to make of his teenage daughter letting a 28-year-old woman stay under their roof, but soon warms to her charms.

There are a number of relationships on the go in this film, and they are all so dysfunctional. At the heart of the problem is Knightley; it's not that she does a bad job, it's just she comes across as the kind of rogue piece of a puzzle that doesn't fit however hard you try to jam it in.

She's not helped by a script that doesn't gel whichever way you look at it. The premise is simultaneously implausible, awkward and just not that interesting. Another obstacle for Knightley is the formidable Rockwell, who breezes in, all guns blazing, as if he's in an entirely different film – or maybe he just wished he was – either way, he's like a tornado on screen, blowing everyone else out of the way.

Ultimately though it's down to director Lynne Shelton, who simply failed as cupid hooking Knightley up with this project.

Like any failed relationship, it's not worth anyone's time to dwell on the mistakes made here, but hopefully Knightley has learnt a valuable lesson about which projects she should, or shouldn't, jump into bed with.