The comic that the upcoming film Avengers: Infinity War will be based on was written by Jim Starlin in 1991 and pits every Avenger against Thanos who, on his quest to court the physical embodiment of Death, wipes out half the universes population from existence. He’s able to do this after collecting all of the infinity stones which are gems of immense power that allow him to manipulate the very fabric of the universe. In the MCU however, these gems have acted as McGuffins in several of the films, so we know that at some point in Infinity War Thanos will have to hunt them down, much to the detriment of several Avengers.
Now that production of Avengers: Infinity War is underway, which is perhaps one of the largest movies ever attempted, many people have begun theorizing certain aspects of the film such as where the film will take place, how the filmmakers will hit some of the important beats of the comic, but it’s necessary to mention that we don’t really know anything about the actual plot of the film. But before trying to figure out what will happen in Infinity War, it’s necessary to point out that Captain America: Civil War, while heavily influenced by the massive comics event, has almost nothing in common with the source material. The themes of the comics are very present in the film but the actual plot is almost entirely different. This is because, while there are many character already introduced into the MCU, the comics universe is so vast and has so much history with thousands of different characters that it’s impossible to adapt it beat for beat. This is why Marvel has been basing their films off of inspiration from many of the comic book arcs rather than trying to completely adapt them for film.
One of the more popular theories is that the Norse god of death Hela, who is played by Cate Blanchett and being introduced in Thor: Ragnarok in November, might take on the role of Death in the Infinity Gauntlet comic. However, the idea that Thanos is in love with the physical embodiment of Death is rather silly so his motivations in the film may be altered somewhat. The point is, we just don’t know. We don’t know how Thanos will get the infinity stones, we don’t know how much of the film will take place on Earth, we don’t know the type of threat Thanos poses, and the list just goes on.
It’s certainly quite astonishing that for a movie of this size, with a cast as huge and famous as this, that we know so little about the actual plot. They’ve been building up to this movie (and it’s untitled sequel) since Thanos first appeared in the first Avengers movie in 2012 but it’s a testament to Marvel and their forward thinking vision that they’re finally giving the fans the conclusion to this epic story and, in the process, been able to build perhaps the largest movie franchise ever.