Few characters are as crucial to the DNA of Avengers: Infinity War as the Vision, played by Paul Bettany. After all, the android has an Infinity Stone in his forehead which may or may not be keeping him alive - but is definitely one of the items Thanos is coming to collect. But just as important is Elizabeth Olsen's Scarlet Witch, because the romance between the two Avengers gives the movie stakes beyond another alien invasion.
So, we guess Vision does kind of figure out how to be human in Infinity War. Image: Disney
"Vision's been on this quest to understand what being human is and I think Scarlet Witch [has], in a large degree, helped him figure that out and what love is," Bettany said last year on the Atlanta set of Infinity War. Then, he broke into song.
"I wanna know what love is!" Bettany sang, channelling Foreigner and the band's hit song of the same name. "I want you to show me!" added Olsen, also singing.
The pair are joking around, but for Vision and Scarlet Witch, Infinity War is no laughing matter. They're dealing with their burgeoning feelings for each other and wrestling with the nature of humanity - all while carrying one of the six things the most dangerous being in the galaxy covets above all else.
"It's gonna be kind of a significant arc 'cause I got one of the stones in my head," Bettany remarked in an impressive understatement. "There's some really bad dudes who want the stone from my head and that's a problem for Vision."
Both Bettany and Olsen acknowledged that film will explore the "very big question" of what happens if/when Thanos takes the stone from Vision's head. And on the day we visited the set last June, there had already been at least one attempt to do just that.
We're wondering where Vision and Scarlet Witch are when this happens. Image: Disney
As we've discussed previously, the scene we saw filmed included several Avengers who had landed on Wakanda seeking help not just for themselves, but for Vision, who had just been attacked. (Read more about the scene here).
"These bad guys are trying to get the stone out of my head and so Wanda and I fought them off, and then we've ended up here for surgery," Bettany said. "I always get confused on how much we can talk about, like are we allowed to explain what we try and do in Shuri's lab?"
"No," the Marvel publicist said.
"No, OK. So forget that bit," Bettany said.
Regardless of what happens to the Infinity Stone in his noggin, the Vision and Scarlet Witch's love story feels like one of the keys that will make Avengers: Infinity War either work or not. "This is definitely the most emotional arc I've done in an Avengers film, that's for sure," Olsen said.
And, unlike most of their fellow heroes, at least these two have each other.
"It just feels like you have something really specific to work with all the time," Olson said of the two. "That feels nice. There's an anchor point to everything, which is what you're constantly looking for when you're doing these movies. ... You have your partner, your life partner with you by your side, and that creates a different kind of stakes, as well."
Those stakes, if we're being honest, probably don't bode too well for Vision - after all, Thanos may fail in the attempt once, but he won't stop until he gets the android's Infinity Stone. Even if losing the stone doesn't kill him, Thanos probably will anyway.
"I just found out what it means to be human and now this Thanos guy," Bettany said. "I think he's a real dick."
Later this week you can read our final interview from the set of Infinity War, in which Anthony Mackie and Sebastian Stan discuss the Falcon and Winter Soldier's role in the film.
Avengers: Infinity War opens April 25.