The biggest mystery on Quantico is not who framed Alex, but why is Elias so obsessed with Simon?

Seriously, dude has been all up in his business since Simon (Tate Ellington) rebuffed his advances in the second episode, doing everything from digging into his apparent nonexistent history in Gaza and scoping out his prescription-less glasses to questioning if he's Jewish and gay. Sure, Simon is pretty shady — or "creepy" — but what is it about him that set Elias (Rick Cosnett) off on this witch hunt?

"Maybe it's some ego because I'm rejecting him!" Ellington tells TVGuide.com. "He's a very attractive man! I do think he's very used to getting things his way. Elias is extremely confident. That rejection could be like, 'OK, there must be something wrong with this guy because why would he reject me? Obviously I'm gorgeous!'"

Fall TV Popularity Contest: Vote for your favorite new show now!

Joking aside, Ellington merely chalks it up to Elias' job as an analyst and not any undercover work a la Ryan (Jake McLaughlin) for Liam (Josh Hopkins). "I do think a lot of it has to do with his training. We will see more of that," he says. "I think that's just his nature of wanting to find something out. He sees the riddle and wants to solve it. He's like a dog with a bone he can't let go of." And after bluntly asking Simon if he's "even gay" last week and threatening to expose him to Liam and Miranda (Aunjanue Ellis), look for Elias to continue his relentless pursuit on Sunday's episode, which could very well change the course of the duo's relationship.

"I'm eager to see the reaction from [Episode] 5 to 6," Ellington says. "I love working with Rick. Most of the time it's a lot of him saying things to me and me looking meanly at him as he leaves the room. But this time is a little different. ... It's one of my favorite moments so far."

Quantico airs Sundays at 10/9c on ABC.

VIDEO: Quantico's Priyanka Chopra reveals the three words that took her three days to learn