In season 2, Archie is confronted by Agent Adams to investigate his girlfriend's dad, Hiram Lodge (Mark Consuelos). This makes absolutely zero sense, for several reasons: Archie is a teenager, has zero real way to infiltrate Hiram's business dealings, and has no reason to aid in this investigation in the first place, save for Adams' general promise that his dad Fred (Luke Perry) will be "protected." (Umm, but protected from what?!?)
Some fans think it's possible that Archie is actually imagining the FBI Agent — and that Arthur Adams, who just so happens to have the same exact initials as Archie, doesn't even exist. That could make sense (in a TV universe, anyway) as Archie was traumatised by all the Black Hood stuff. Maybe an FBI Agent watching over Riverdale was one way for Archie to cope with all the drama.
However, it's not the only explanation for why Archie is the only person around when Agent Adams is. What if Adams is actually a straight-up ghost, and Archie is the only person who can see him?
This might sound like a ridiculous fan theory, and uh, it could very well be one. But let's not forget that ghosts do hang out in Riverdale from time to time. In the episode "Tales From the Darkside," Archie sees what appears to be a ghost of a deer: The carcass of the animal is then shown on the back of a pickup truck. It's a small moment, but it could, potentially, be foreshadowing some greater power that Archie has yet to discover.
It's also not the only instance of supernatural rumblings on Riverdale. For one thing, Riverdale exists in the same universe as Greendale, the town from comic book The Chilling Adventures of Sabrina, in which supernatural stuff is commonplace. (A TV series based on the comic, penned by Riverdale show runner Roberto Aguirre-Sacasa, is in the works at Netflix.) We have also seen Cheryl (Madelaine Petsch) have visions of her dead brother Jason (Trevor Stines). It's even implied that Nana Blossom (Barbara Wallace) has some witchy powers of her own.
Now let's go back to everything we know about Arthur Adams. It's not much, but we do know that he grew up in Riverdale. The town is pretty small, and it's suggested that people don't tend to leave that often. Assuming Adams is being honest here, why wouldn't he run into some old friends in town, who could help him with his case? Maybe it's because he's not alive.
Dun dun duuuuuuunnnnnnn.
Look, I know what we're all thinking: If anyone was going to see dead people on Riverdale, it would be omnipresent narrator and self-proclaimed weirdo Jughead Jones (Cole Sprouse). But hey, anything is possible in this town, right?