The latest adaptation of Young Adult sci-fi (Hunger Games, Divergent, The Host, Ender’s Game, Mortal Instruments, The Giver, and The Maze Runner being a recent handful), this Red Dawn meets They Live meets Ender’s Game sci-fi romance drama occasionally interests but ultimately never really gets off the ground.

Cassie (Grace Moretz) was your typical sixteen-year-old living a typical sixteen-year-old’s life when a mysterious alien mothership hovers over her hometown and unleashes waves of attack: first an electromagnetic pulse kills all power, then earthquakes induce tsunamis, with those who make it inland battling an Avian Flu epidemic. Then comes the fourth wave: infiltration, with the aliens taking human hosts to wipe out the remaining survivors. What’s left of the army, under Col. Vosch (Schreiber), rounds up children and trains them to spot and destroy those posing as humans with school football hero Ben (Robinson) proving himself a worthy squad leader. When Cassie and her kid brother (Zachary Arthur) are separated, she, teaming up with loner Evan (Roe), makes it across dangerous terrain to reach him before the expected fifth wave strikes, whatever that might be…

There are some things to admire here with director J. Blakeson – writer/director of The Disappearance of Alice Creed (woo-hoo) and writer of The Descent Part 2 (boo) – doing his best to run a tight ship. When Ben is told the kid on the opposite side of the glass is an alien and is ordered to kill him it echoes the Milgram Experiment. And it doesn’t have anything good to say about the army who use scare tactics to mould and condition children to become killers: “We didn’t get rescued, we got drafted!” Big issues for a kid’s movie. A scene where screaming workers race up a flight of stairs as the tsunami fills the stairwell is exciting. Splitting the narrative in two – it’s as much Ben’s story as it is Cassie’s – is unexpected.

But in its determination to tick as many boxes as it can – namely the romance box – the story (adapted from Rick Yancey’s novel by heavyweights Akiva Goldsman and Susannah Grant) comes undone. Would you really be texting about some hot guy when there’s an alien spaceship a few hundred metres skyward? Would you really be stopping for a kiss when you’re desperately seeking your kid brother in a building that’s falling down? It’s patronising moments like this that undercut the Strong Female Role Model it sets up so well: that after invading aliens, after dead parents, after bullets in the leg, after missing kid brothers, what all girls really want is a hot guy. I’m not buying that. The twist makes zero sense too.

And disappointingly Chloe Grace Moretz is a problem. Terrific in Kick Ass, Let Me In, Carrie and The Equalizer, the eighteen-year-old struggled with the more dramatic moments of If I Stay and is found wanting here too. She doesn’t convince as a girl on the edge but maybe that’s down to the conflicting motivation: does she want to save the world or see Roe with his shirt off?