What is a logline?: a brief summary (25 to 40 words) of a story for film, television or book that states the central conflict and an emotional "hook", with the purpose of stimulating interest (Wikipedia).
A logline is evaluated not exactly for what a story is (since it does not contain a complete story), but for what it can be. Suggestions usually seek to maximize the dramatic potential of the idea.
Title: Endless Night (feature-film, drama).
Logline (27 words): Death has until dawn to ensure his very survival by splitting a couple whose determination in preserving their toxic relationship threatens to shred the fabric of time.