Avengers 2 doesn't open for another few weeks, but deep inside Marvel headquarters they've already begun turning their attention to the next big movie: Captain America: Civil War. Frequently referred to as Avengers 2.5 because of the sheer amount of superheroes packed into this one film — Captain America, Iron Man, Black Widow, Falcon, Black Panther, Spider-Man and Hawkeye are all confirmed to star — the third Captain America movie might be the biggest superhero film yet. As Marvel gets ready to begin filming, a casting call has given us our first look at the film's plot.

According to Screenrant, Captain America: Civil War is looking for extras who live in or around the Atlanta area to join the production, which is scheduled to begin on April 1. In addition to Atlanta, Anthony Mackie previously confirmed that the film would also shoot in Puerto Rico and Berlin. (Berlin makes sense because of the Hydra/Baron Zemo connection, but Puerto Rico is an interesting addition.)

April 1 seems awfully ambitious, especially considering that stars Chris Evans, Robert Downey, Jr., Scarlett Johansson and Jeremy Renner will still be out promoting Avengers 2. But, with a May, 2016 release date approaching, Marvel can't wait much longer. (Remember, Batman vs. Superman opens in March of 2016 and wrapped principal photography months ago.)

The casting call included this brief synopsis, most of which we already knew or assumed based on the existing comic line, but it's interesting to note that it won't just be Captain America and Iron Man going to war against each other.

Following the events of Age of Ultron, the collective governments of the world pass an act designed to regulate all superhuman activity. This polarizes opinion amongst the Avengers, causing two factions to side with Iron Man or Captain America, which causes an epic battle between former allies.

What's interesting is that this is only part of the plot of Civil War. There's still the issue of Cap hunting down Bucky/The Winter Soldier, the return of Crossbones (Frank Grillo) and the introduction of Baron Zemo (Daniel Bruhl). That's a lot of stuff to go down in one superhero. But, Marvel was determined to top Batman vs. Superman and the introduction of the Justice League, and this might just be the way to do it.

Captain America: Civil War opens in theaters on May 3, 2016.