Where Is The Soul Stone?

SPOILER ALERT* (we published this post prior to the movie, and we were not right about anything concerning the soul stone's location. As it turned it out, there was nothing in any previous Marvel movie that would have suggested this outcome. What happened was impossible to predict from the MCU)*

Marvel Studios has been building back story on all the "Infinity Stones" for years across several franchises, and we have been introduced to all of them and are aware of their current location heading into the film. Well, all except one, the soul stone. The one gem that Thanos needs to wipe out half the life in the Universe by snapping his fingers. Not only has there been no clues, but they haven't even said its name or openly acknowledged that it exists.

So where is it? The answer should be obvious, but maybe it's too obvious. Heimdall, the Asgardian with orange eyes who can see people's souls across several light years. In three Thor movies, he frequently uses the word "soul" talking about how he can see people's souls across the galaxy. That's quite a substantial power to have. In Ragnarok, Heimdall was able to teleport Thor's soul across many light years back to Asgard. This would seem to be an obvious power to have if possessing the soul stone. The character is played by beloved actor Idris Elba, so it would be gratifying cinematically to have a man like Elba holding one of the most precious stones.

Whenever a character is in the possession of an infinity stone, their eyes change colour. This has been recurring theme throughout the entire MCU. For example, when Loki uses the staff which was later revealed to hold the mind stone, mind controls Hawkeye and Dr Selvig, there eyes change to blue. In Thor Dark World, Malikieth and Jane's eyes change when they are infected with the reality stone. In Guardians of the Galaxy, Starlord's and Ronan's eyes change to purple when holding the power stone. Heimdall's eyes were always the greatest clue that he has the soul stone.

If all those supposedly obvious soul stone related clues were just misdirection and Heimdall doesn't have it, then where could it be? There is speculation that Ironman has the soul tone because of the colour orange in some promotion material, but that's very weak evidence. There has not been any indication that Tony might be in possession of the soul gem. There is also speculation that the gem is on Thanos home planet of Titan, because we see it in a trailer with an orange hue. It's an unlikely scenario, but it's also the best theory if Heimdall doesn't have it.

There is a new trailer that shows at least 4 gems (power, reality, space, and soul) on the gauntlet when Thanos arrives in Wakanda (it's difficult to see if the mind gem is on the thumb). This trailer marks the first time we have ever seen the soul gem in the MCU. They have CGI'd gems off the gauntlet for some trailer footage, but I don't believe they would CGI them onto the gauntlet. Ergo, Thanos will get the soul, power, space, and reality gems before travelling to Earth. It now seems very likely that he will get both the space and soul gems in the beginning of the movie when the Asgardian ship is attacked.

Update:  There has been speculation that Captain America might have the soul stone based on the colour of his eyes. We know now that Hiemdall most likely has the soul stone. Claiming that Cap's eyes are orange is not sufficient evidence. This just the reflection of the gauntlet.