Warning: Spoilers for Trigun Stampede, Episode 7Anyone watching Trigun Stampede has surely noticed that Vash isn't the average guy. Only now, though, is that difference being explained to the characters.
Vash (Trigun's titular Stampede) stands out for a lot of reasons--his mechanical arm, for starters, as well as his unwillingness to kill or even harm others in defense of himself. It's also been shown that Vash doesn't really age, as evidenced by a photo of him from around 20 years ago in which he looks exactly the same as he does today. In episode 7, while trying to stop the Sand Steamer from crashing into the city of Hopeland, Vash goes down to communicate with the power source of the ship--the Plant. When Meryl and the others find him, however, they discover that he's covered in Plant-like markings, too, exposing his secret.
Vash is Actually One of Trigun's Plants
In Trigun Stampede, Plants are a special type of alien creature that can be used as a power source, and that power is essential to survival on No Man's Land. Often compared to angels for their beauty, most Plants aren't intelligent, or so it seems, but some are--and the most noteworthy among them in Trigun are Vash and Knives. Knives has been stealing and collecting Plants from settlements because he sees them as his kinsmen, even though they're not intelligent, and resents humanity for what they've done to the Plants. Vash is able to recognize how essential they are, and while he does sympathize with them, feels they must remain where they are, where they can do the most good.
Episode 7 sees Vash descend to the Sand Steamer's Plant room, and Vash begins trying to communicate with the creature behind the glass, attempting to get it to shut the ship down before it can crash. When Meryl and the others walk in, they see Vash touching his hands against the glass where the Plant's hands are--and when he turns around, there are glowing lines across his face, matching those that the Plant has on its face. Meryl recognizes what this means immediately, but the episode ends before they can react. Meryl was already suspicious after seeing Vash hadn't aged in 20 years, so this really only confirms her suspicions.
The question now is how the other characters will react to this news. Vash is still the same person, who tries to do good despite trouble following him everywhere he goes. Will this revelation cause them to treat Vash differently, or is the "how" less important than the "why?" The answer to that only lies ahead in the next episode of Trigun Stampede.
Trigun Stampede debuts new episodes on Saturdays, via Crunchyroll.