Your main character, the hero of the story no matter the genre, must be isolated to make a logical, powerful story.
I don’t mean stranded on a desert island isolated, but cut-of-from-help isolated.
Consider, your hero encounters a problem in the first act of the story. We learn who the hero is, what their normal is, and then something happens… this is the inciting incident. What happens next is the isolation of your hero. It isn’t enough for the problem to be solvable, it must only be solvable by the hero.
Such isolation takes on many forms. It could be they (the hero and the merry band of support characters, or the ensemble) are literally cut off. Their plane crashes in the dinosaur-infested jungle and there are no other humans for miles.
Or it could be a matter of skill set. The president is dying on Air Force One and the hero is the only doctor. It all on the hero.
It could be relational. The hero estranged from his dying father is the only one who can fulfill his last request. Or a terrorist will only deal with the hero, no one else.
This is vitally important because, hey, if there is someone better suited to save the day, why is your character the hero?
This is particularly difficult in today’s society where everyone has a cellphone. You either need to get rid of the phone, out of range, broken, or dead battery, or isolate through time; there are others more suited, but they don’t have time to get there, or are unmotivated, or in league with the villain.
How is your character isolated? Make sure it’s clear and strong or your story will be unbelievable.