Radius lured me in with an interesting premise, but I stayed for the characters.
While watching this I came up with many versions of what was actually happening, but in the end the explanation itself was not required for me to enjoy this.
I liked the characters, their arcs, and the fact that the story was built around them. The writing was not as stupid as in many low budget sci-fi films, yet I can't really call this a sci-fi film, can I?
I mean, it was clearly marketed as a sci-fi mystery and even the titles suggests something like that, but it's actually a completely different movie.
Don't approach this as a sci-fi film with an easy explanation and if you enjoy emotionally packed films you will like this one.