It has been there, right in front of us, since 2011.

Marvel’s long game, its plan for its big-screen universe, through the next several years.

2011 is when “Thor” came out, and figuring prominently into the plot were MacGuffiins – the objects of desire that spark movie plotlines, rare and powerful objects like the Casket of Winters and other arcane weapons in the arsenal of Odin in Asgard.

Marvel gave us another big hint that same summer, as “Captain America” fought the Red Skull to possess the Tesseract, also known as the Cosmic Cube. Another artifact of power. The Tesseract even showed up at the end of “Thor.”

The Tesseract, lost when the Skull’s airship went down in the ocean after Captain America defeated the villain, figured prominently into 2012’s “The Avengers.” In Loki’s hands, the cube opens a portal that allows an army assembled by Thanos, a cosmic villain, to attack Earth.

Thanos. That smiley purple guy who appeared in the mid-credits scene at the end of “The Avengers.”

Now that Marvel has announced that the next “Avengers” adventure, 2015’s “Age of Ultron,” will be about Ultron, the robotic villain, it became clear that Marvel and Joss Whedon didn’t put Thanos at the end of “The Avengers” for no reason. They were, obviously, building to something bigger for the third “Avengers” movie. And they were laying it out for us to see.

Remember, in “The Avengers,” when Nick Fury asks Captain America about the Tesseract, Cap replies, “You should have left it on the bottom of the ocean.”

Okay, so items of great power. Check.

Here’s where we get to the spoilers for “Thor: The Dark World,” which opens this Friday. So don’t continue reading if you don’t want to know. But it’s essential to my theory about Marvel’s long-term plans.

Ready?

There are two end-credits scenes in “Thor: The Dark World.” The latter scene, at the very end, is a nice character moment and establishes that Thor’s relationship with Jane Foster will continue.

But it’s the mid-credits scene that sets up several years worth of Marvel movies.

In that scene, Sif and Volstagg, two of Thor’s cohorts, have possession of the Aether, a powerful MacGuffin that plays into the plot of “Thor: The Dark World.”

Thor and his allies have captured the Aether and, in the end credits, Sif and Volstagg take the Aether to the Collector, a longtime Marvel Comics character played by Benicio Del Toro, who just so happens to play the same character in “Guardians of the Galaxy” the Marvel movie coming in late 2014.

Thor’s allies give the Collector the Aether and note the Tesseract is in Odin’s arsenal.

“It’s too dangerous to have two Infinity Stones in the same place,” they say.

Six Infinity Stones, or gems, are the power source for the Infinity Gauntlet in Marvel comics. It is a tool and a weapon of … Thanos.

After Sif and Volstagg leave, the Collector says the words that set the next several years worth of Marvel movies on their path:

“One down, five more to go,” he says.

In the comics, the Infinity Gems were not artifacts like the Cosmic Cube or Casket of Winters. They were literal stones or gems, albeit with supernatural powers.

Now consider the plot description Marvel released last year when it announced “Guardians of the Galaxy:”

“In the far reaches of space, an unlikely cast of characters including an American pilot and a group of futuristic ex-cons go on the run with a highly coveted object and must join forces to defeat a cosmic force of epic proportions.”

What highly coveted object? Possibly another Infinity Stone?

It now seems apparent that the Marvel movies are pursuing the years-spanning storyline of Thanos trying to acquire the powerful Infinity Stones and the Avengers, Guardians of the Galaxy and other heroes trying to foil his plans … coming to a theater near you in “Avengers 3,” maybe in 2017 or 2018.

In the meantime …

Marvel movie universe mastermind Kevin Feige has been quoted recently as hinting that the company has its movies roughly planned out into 2021 or so. Considering that’s only three years after the third “Avengers” film completes Phase Three of Marvel’s big screen plans, it’s probably not surprising.

Okay, so bonus round: What’s Marvel planning through and post Phase Three?

What could possibly top the showdown with Thanos?

(FYI, I’m not counting the movies based on Marvel characters that the company doesn’t have the rights to for the screen, so there’s no mention of “Spider-Man” or “X-Men” movies here, although those are certain to continue, as likely will “Fantastic Four” films.)

So here’s the rough timetable as we know it so far.

2014: “Captain America: The Winter Soldier,” “Guardians of the Galaxy.”

2015: “The Avengers: The Age of Ultron,” “Ant-Man.”

2016: Two still-unspecified Marvel films.

2017: One still-unspecified Marvel film, with at least one more likely to come.

2018: The third “Avengers” film maybe, if they continue to turn them out every three years.

Mentioned as likely or possibilities: “Dr. Strange,” “Black Panther.” Possibilities since their rights have reverted to Marvel: “Daredevil” and “The Punisher.”

Also almost certain: “The Inhumans,” about Marvel’s other race of super-powered beings besides “The X-Men.”

Any of these movies would be fine post-Phase Three fare.

And any of them would be appropriate for shoe-horning into the Phase Three build-up to the third “Avengers” movie.

Maybe they’ll turn up in one of those 2016 films, or one in 2017 or 2018.

I don’t know about you, but I’m planning to be there.