Hi dpg,
I agree about the plot conspiracy: I just said that the conspiracy is against people; as it is for example in Mars Attacks, Independence Day or The Day After Tomorrow.
But not about the unity of action and the principal character: There are several heroes and no unity of action in most of disaster movies.
In some of these, the heroes do not even meet each others throughout the whole movie! (Mars Attacks...).
In the easiest cases, the main hero is the one who triggers the final victory (Independence Day); in some others, there are two or more main heroes (The Tower Inferno)...
I have several main heroes who don't meet each others throughout the whole movie*. This is why I don't know how this damned logline can be summed up in one sentence!
*Auctually, some of them get organized via networks to make good decisions and lead this sudden change.
I'm still working...
All the best.