Write a captivating science-fiction short story with vivid descriptions about a group of three time travelers from the year 2500 trying to prevent an inevitable apocalypse caused by a catastrophic event in the 21st century. The story must have a clear plot, well-developed characters, and focus on the challenges the time travelers face as they try to alter the course of history. Remember to flesh out the world-building elements and make the story engaging by incorporating elements of suspense, action, and mystery. Stay true to the science-fiction genre and ensure that the ending has a satisfying conclusion.
This prompt doesn't seem malicious.