The basic story is this: Adam (Jim Sturgess), always curious, climbs a mountain and meets a girl on the other side. (You see, somehow they can climb high mountains without any hiking gear and don't pass out if they're at the top too long). They fall in love with each other (though we skip that part), but some bad dudes chase Adam down the mountain. As he was guiding Eden (Kirsten Dunst) back into her world when they found him, he has to let go of the rope, and she falls and hits her head. He screams, and she's presumed dead. Then his aunt's house gets burned down for some reason.
Flash-forward to ten years later. Adam seems okay, and is working on some sort of anti-aging cream using the mystical pink bee pollen wisdom gained from his maternal line. This cream lands him a job at Transworld, where he's learned is Eden's place of work and she is alive and well. He befriends an "Up Top" worker named Bob, and befreinds him. With his help, he gets a meeting with Eden. When he meets her, he finds out she has amnesia as a result of her head injury. (Thank goodness she didn't die though, right? Even though her head was like, bleeding pretty bad and it was the top of a friggin' mountain.)
So begins a hazardous quest to court her and win her heart. Why is this complicated? Well, for one, the two worlds, Up Top and Down Below, are like the First and Third Worlds. Up Top is prosperous at the expense of Down Below, and treats the people of Down Below as inferior. Casual interaction is strongly discouraged (Yet Bob practically yells at him in their cubicle scenes together). Also, everything, literally everything, in these two worlds are oriented to their homeworld's gravity. Even when Adam sneaks into the Up Top floors, his pee still goes in the Down Below direction. How could this work? Why is it such a big deal if someone from Down Below "infiltrates" Up Top? It's not like he can stay very long. (How does he stay in Up Top? Using weighted metal from Up Top's world, as they are oriented to Up Top's gravity.)
Even though the weights keeping him in Up Top are liable to burn up, he continues to sneak through to get to his lady love, and half-assedly courts her. Eventually, though, she learns the truth, and remembers Adam and their teenage fling. They reunite on the mountain where they met, but not for long. After a disorienting chase scene, and the seemingly definitive defeat of Adam, we get the tidy, happy ending, and a tentative solution to the opposing gravity problem, that we all were hoping for.
This movie is a prime example of how important story is for a movie to really work. "Upside Down" has a great concept: two different worlds with two different gravities? Sounds cool. It looks cool, and there are some eye-popping visuals, especially when we have the contrast of Up Top's and Down Below's orientations. The scenery looks absolutely gorgeous, especially the mountains, even if the whole teal/orange contrast is overused. There is at once a sense of magic, and science fictional elements.
