[Warning: This article contains spoilers about Sunday's episode of Quantico. Read at your own risk!]

Keep your friends close and your enemies closer, right?

We don't know for sure if Shelby (Johanna Braddy) is the culprit behind the attack on Grand Central Station on Quantico, but she is definitely the biggest suspect so far after Sunday's episode.

Seemingly playing both sides, Simon (Tate Ellington) flouts Clayton's (Mark Pellegrino) order to keep Alex (Priyanka Chopra) in her makeshift evidence shed and instead takes her to his lusciously bearded bomb-maker pal to look at the piece of wire that was in the bombs. Bearded bomb-maker pal drops his own bombshell: The wire was made by Shelby's family's company.

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Team Simex breaks into Shelby's home, to which Shelby inevitably returns minutes later. Guns drawn, Shelby tells Alex that Simon is with the FBI, while Alex accuses her former bestie and roomie of framing her because "your whole world fell to pieces when I found out the truth about your parents." Shelby claims it's "insane" and "impossible" that she blew up Grand Central because she was out of the country and the seven bombs were buried and could've only been detonated within a two-block radius, not remotely. When Ryan (Jake McLaughlin) joins the party to inform them that the FBI was en route, Alex makes the boys leave and proceeds to beat up Shelby. They evade the FBI by hiding in Shelby's car right in front of her house, where the FBI APPARENTLY DOES NOT LOOK. These guys make the FBI on The Following look like geniuses, eh?

Alex then holds Shelby hostage back inside the house. "You're gonna tell me how this wire from your family business ended up as part of those bombs," she says. "I will wait as long as it takes."

Is Shelby the mastermind? This early in the season, probably not. The more intriguing mystery is the deal with her family. What's "the truth" about her parents? Did they not die in 9/11? In the past story line, Shelby and Alex bond over heart-to-heart confessions. Alex shares that she was the one who shot her dad and Shelby says that her secret phone calls are with her half-sister, whom she did not know existed until her parents died. Since she lied about her parents, is she lying about this too? If her sis is real, was she behind it... or an accomplice?

Other important reveals in the episode:

PAST
- O'Connor (Josh Hopkins) tells Ryan that Alex has been flagged as an unfit candidate for the FBI, so his only job now is to get her to quit the academy. "She's more fragile than you think," he says. This is true, as Alex, still reeling from having learned that her dad was a "hero" in the FBI, basically psychs herself out in a shooting exercise. Ryan instead goes to Miranda (Aunjanue Ellis), and they both convince Alex to stay and refocus because even though her dad was a great agent, he was an ass in real life. (Side note: Alex should've never felt guilty about killing a "hero" in the first place and it's lazy that this was the given reason. He abused your family and you shot him in self-defense!) O'Connor later confronts Ryan and tells him that he's not undercover, but on probation. "You are officially retraining and if you fail outta here, you are out," he says. "So do whatever you want with the assistant director. She can't save you." Oh, but maybe she can. Miranda has been listening to the whole conversation!

- Miranda tracks down Nimah (Yasmine Al Massri) at a dingy motel and convinces her to return by revealing her master plan. Turns out her super creepy incarcerated son was roped in by extremists and they had planned to attack his high school, which counted Congress members' kids as students. Thanks to her pull, he's only serving two years in juvie and as he revealed last week, he's up for parole. "I hope he doesn't get it," Miranda says. "The people who reached out to my son, they're reaching out to others. ... We need to infiltrate their network. ... I need you both. I need you to work together as one."

- Elias (Rick Cosnett) continues his inquest into Simon, learning that he has no history in Gaza with the UAWC, and asks three burning questions. "Are you a patriot? Are you Jewish? Are you even gay?" Simon: "The answers are yes, definitely and no. But my boyfriend is."

Everything you need to know about Quantico

PRESENT
- Ryan tells Nathalie (Anabelle Acosta) that he went to Alex's that morning to clear the air because he hadn't talked to her since she "found out about us."

- Simon, who's been undercover with the FBI for months, is Team Alex all the way, he insists to a peeved Ryan. "If my allegiance was to the FBI, you and Alex would both be in handcuffs right now," Simon tells him, while Nathalie suspiciously observes their intense convo. Subtle, guys.

- Since Alex has been in the wind for so long and has taken Shelby hostage, Clayton tells his team, "From here on out, it's shoot to kill." Too bad the person with the best shot is handcuffed to her stairwell.

What did you think of the episode? Do you think Shelby's innocent? Is Simon truly with Alex?