Your difficulty to construct a logline that accurately describes this concept sheds doubt on the integrity of the premise. In other words, without significant change I think this is too complex to work as a story for a feature film, perhaps other mediums such as graphic novels but not as a single plot for a feature.

Sorry if this comment seems harsh, but it’s truly what I think. Consider a producer reading this logline, they would be expected to extrapolate the sequence of events in your story, but there are too many unclear elements.

The story starts with a bio-sphere experiment already running (a big leap of logic but possible). The main characters (two MCs already raises alarm bells in most producer’s minds) “…manipulate…” what does that mean? Change the temperature of the atmosphere? Drug the food and water supply? Screw with the daylight hours? This statement is both unclear and crucial for the story.

What does “…end up sabotaging each other…” mean? Alter the data collection programs they use? Directly interact with the inhabitants? Again, this is a plot-critical action that’s simply unclear.

Lastly, you write that they get locked inside, but how? Why? And most importantly of all, to what end? This sounds like the inciting incident, and as such, makes all that came before it redundant. Now that they are locked inside their own experiment (a nice bit of irony by the way) what are they going to do? Or in other words, what’s their goal?

I suggest you rethink the concept and start it from the point of the scientists being locked inside their own experiment with a clear goal – perhaps they want to break out or find a way to terminate the experiment from within.