This photo provided by Disney/Marvel shows, Chris Evans, left, as Captain America/Steve Rogers, and Chris Hemsworth as Thor, in the new film, "Avengers: Age Of Ultron." The movie releases in U.S. theaters on May 1, 2015.

This photo provided by Disney/Marvel shows, Chris Evans, left, as Captain America/Steve Rogers, and Chris Hemsworth as Thor, in the new film, "Avengers: Age Of Ultron." The movie releases in U.S. theaters on May 1, 2015.

Jay Maidment/Marvel

Marvel's latest blockbuster is about to hit theaters, and there's a lot going on in it. You can go into it purely for the action sequences, and that's fine, but if you care about the characters and the plot, you might need a little help.

While you should definitely watch the original Avengers movie before seeing its sequel, Age of Ultron, it won't be enough to see the full picture. It may sound a bit crazy, but if you haven't been watching Marvel's other movies (Captain America: The Winter Soldier in particular) then a few aspects of the plot are going to be very confusing for you.

Yeah, Thor, Captain America, Guardians of the Galaxy, Agent Carter, Agents of S.H.I.E.L.D. ... They all nod to each other in various ways -- some small, some huge -- and they're all leading up to the next big Avengers experience: The two-part Infinity War epic, due out in 2018 and 2019.

Not caught up? Don't worry. After watching Age of Ultron, I have a good idea of what you need to know.

Minor spoilers for Age of Ultron might follow. Major spoilers for other Marvel films definitely will.

First off, no, there's no post-credits scene. But ...

Joss Whedon wasn't lying. There isn't anything extra if you sit through the credits (sorry, Spider-Man does not show up). There is, however, a very brief mid-credits scene that happens shortly after the credits start rolling. It's nothing terribly surprising, but it does set the stage for what's to come.

Hail Hydra

One of the biggest events in the Marvel Cinematic Universe so far -- and the one that has most affected where the Avengers stand in Age of Ultron, is the rise of Hydra. As seen in Captain America: The Winter Soldier (and running in parallel, Agents of S.H.I.E.L.D. on ABC), the terrorist group of ... well, Nazis, basically, infiltrated S.H.I.E.L.D. for years and nearly destroyed it from the inside.

So while the first Avengers film ended with our heroes basically on top of the world, they've fallen from grace considerably in the time since we last saw them. Sure, they still have Tony Stark's considerable finances and influence, but there were a lot of losses. The biggest casualty was trust, as even many high-ranking S.H.I.E.L.D. members were secret Hydra members all along.

So where did that leave Nick Fury?

At the end of Winter Soldier, most of the world is under the impression that Nick Fury is dead. He takes the opportunity to back away (a bit, at least) from his role as the leader of all things S.H.I.E.L.D., leaving him with a lot less power than he's had in Marvel films past.

What are all these stones that people keep talking about? They seem important.

Ah, the Infinity Stones. They've been popping up in Marvel's movies for a long time, though you may not have always noticed them. They're setting the table for one big end-game: Avengers: Infinity War, which will be a two-film adventure several years from now.

To put it in simple terms: the Infinity Stones (Infinity Gems in the comic universe) are six objects that are incredibly powerful objects on their own, so you might imagine what could happen if somebody got their hands on all six. The nearest fantasy/sci-fi comparison might be the rings in Lord of the Rings, though there isn't really "one stone to rule them all." They're all pretty destructive.

The stones got the most attention before now in Guardians of the Galaxy. One stone in particular was central to that film's plot, but the other stones are out there -- as Age of Ultron will make sure you know.

Who are these sidekick characters showing up with Iron Man and Captain America? One of them has wings?

They're... Iron Man and Captain America's sidekicks. You nailed it. They're War Machine and Falcon (you can probably guess which is which), and you learn more about them in the other movies.

My nerdier friend told me that some Ant-Man character created Ultron, but that movie isn't out yet and I don't even know if I want to see it, so ...

This movie rewrites that history. In Avengers: Age of Ultron, Tony Stark is the one playing God with robots. A bummer for the huge Ant-Man fans out there, but it simplifies things significantly. There are no Ant-Man references (at least, none that I caught) in Age of Ultron.

Who are these new characters, Quicksilver and Scarlet Witch? I'd swear there was a character called Quicksilver in another recent comic book movie.

There was, and it was the same character... Sort of. Quicksilver showed up in X-Men: Days of Future Past, but it was a vastly different take on the character. His name was still Pietro Maximoff, and he still ran really fast, but there was no mention of his magical sister. Since Fox's X-Men film franchise is entirely disconnected from Marvel Entertainment's cinematic universe, you don't need to worry about that version of the character.

I could give you a long, complicated history of who the Maximoff twins are in the comics, but it wouldn't serve much purpose. You get plenty of their story in Age of Ultron.

This photo provided by Disney/Marvel shows, Aaron Taylor-Johnson, left, as Quicksilver/Pietro Maximoff , and Elizabeth Olsen as Scarlet Witch/Wanda Maximoff, in a scene from the film, "Avengers: Age of Ultron."

This photo provided by Disney/Marvel shows, Aaron Taylor-Johnson, left, as Quicksilver/Pietro Maximoff , and Elizabeth Olsen as Scarlet Witch/Wanda Maximoff, in a scene from the film, "Avengers: Age of Ultron."

Jay Maidment/AP

The term "enhanced" keeps coming up. Huh?

You can probably guess. When characters in Age of Ultron refer to "an enhanced," they're referring to someone with seemingly supernatural abilities -- like most of The Avengers. Agents of S.H.I.E.L.D. typically calls them "powered people." The Maximoff twins fall under this category.

Speaking of Agents of S.H.I.E.L.D., do I need to be caught up with that?

Agents of S.H.I.E.L.D. was not a great show when it started. I won't lie, I personally gave up on it a few episodes in. However, it got really good halfway through the first season (after Thor: The Dark World and particularly after Captain America: The Winter Solder), so I'd say it's worth it for the die hard fans. If you're just a casual fan of super hero movies, though, it's not necessary.

If you watch the show, however, you should probably make sure you're caught up before seeing Age of Ultron. There's nothing too major, but the end of the episode "The Dirty Half Dozen" does lead directly into Ultron.

Can't you, just, like, tell me what happens in that episode so I don't have to watch it?

Eh, fine. Spoiler alert.

After raiding a Hydra base and stealing some data from their computers, Coulson tells Maria Hill that he's found the location of Loki's scepter -- a weapon S.H.I.E.L.D. desperately wants to get away from Hydra hands. With this info on hand, he tells Hill "it's time to bring in the Avengers."

Meanwhile Raina, who appears to have the growing ability to see into the future, warns "Men made of metal will tear our world apart and the world will be changed forever."

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