Saoirse Ronan plays Melanie, a teenage rebel against an invasion by aliens - the Seekers - who control the minds of their human victims by placing parasitic "souls" into their bodies. When Melanie is hunted down by vengeful seeker Diane Kruger, she finds herself accommodating two people - herself and alien invader Wanderer. However, her extra-terrestrial interloper is gradually won over and the pair of them - in one body - flee to join a guerrilla group hiding out in the desert. Writer Stephenie Meyer's Twilight follow-up will appeal to the same teen audience with the novelty this time of two hunks fighting for two girls... inhabiting the same bod.
After anaemically reworking the vampire legend into a soppy yet stellarly successful teen romance with the Twilight series, it was a matter of some conjecture which genre Stephenie Meyer would appropriate for the next woozy love-in.
She's plumped for sci-fi banker "alien invasion" in a yarn that's heavier on the romance than the action as Invasion of the Body Snatchers is seemingly reworked by Mills & Boon Jr.
On the plus side, director Andrew Niccol (who also adapts the source novel) has cast Oscar-nominated Saoirse Ronan (Atonement) as the lead, a cheerier choice than the grumpy-pants who grimaced her way through the Twilight series like a truculent teen dragged round a museum.
However, compared with the genuine thrills and emotional heart of The Hunger Games, this is a flaccid affair whose modest budget ($40m) is all too apparent thanks to glossy TV movie production values and the feel of something that could have done with a little more polish.
Ronan is its main strength as Melanie, a rebel human who is hunted down by white-suited goons led by the Cruella de Vil-like Seeker (Kruger), who plants a "soul" in her mind in the hope that it will lead to the resistance, including her boyfriend, bolshie hunk Jared (Max Irons).
Melanie's consciousness and that of the 1,000-year-old alien interloper - Wanderer - succumb (after a handbags-in-the-brain-at-dawn stand-off) to a raw understanding which sees them fleeing the Seeker's HQ and heading off to the desert where they hook up with the rebel group in a subterranean base beneath the mountains.
However, Kruger isn't far behind and is determined to winkle them out. Then there's the added complication of Jared renewing his passion for Melanie while his buddy Ian (Abel) starts to get the hots for Wanderer (or Wanda, as she is now called). So, what we have in prospect is the most bizarre ménage à trois in the history of cinema.
Unfortunately, we don't get it. What we do is get a couple of limp action set-pieces (a freeway chase is possibly the most 'mehr' moment you'll see this year), stolen kisses in caves that look like they once did service in Blake's 7 and dialogue that sounds like it truly wafted in from another world. Probably Planet Naff.
You never for one moment believe - or, more crucially - care about this (the sci-fi element is confined to a fleet of chrome-plated Lotuses, silver contact lenses and a wardrobe of white suits) and the narrative is little more than a dull alien invasion story injected with a shot of syrupy romance.
Still, it's the sort of syrupy romance Twihards will lap up...even if it makes the rest of feel a little queasy.