Amanda Schull on "12 Monkeys"   SOURCE: Syfy

Now that the Season 2 finale has been unveiled with a cliff-hanging mic drop that changes everything, one key question lingers: Did you see it coming?

According to series star Amanda Schull, the whole “ending at the beginning” clue had fans speculating wildly on the identity of The Witness. Read on for the jaw-dropping reveal that ended Season 2 on Monday (July 18). But beware: The ‘Mother!’ of all spoilers lie ahead.

RELATED: ’12 Monkeys’: Who is The Witness?

“Isn’t that creepy, how it came out?,” Amanda says to Zap2it about the episode’s big reveal. Dr. Cassandra Railly is pregnant in 2163 with The Witness — a point punctuated by hundreds of faceless devotees chanting, “Mother! Mother!”

According to Schull, the horrific moment was even more bizarre on set. “They weren’t saying anything as we shot it. Those guys couldn’t see through their masks, first of all. Then, maybe because of union rules or because they wanted Tom Noonan’s voice, when we were shooting it all I heard was Tom’s voice saying, ‘Mother! Mother!’ repeatedly. When they added in the other voices … wow that was creepy.”

So, how does it feel to drop this bombshell on the ’12 Monkeys’ audience? Schull laughs in realization of its power. “I really like how it came out,” she says. “When Terry [Matales] told me a while ago that this was his vision, we discussed it. The fact that I got to spend so much time detesting The Witness, feeling like he’s responsible for so much horror … then you find out that the person she loves and feels a connection to, Cole — that she and him have created this hideous being? Hopefully that realization is just as horrifying for the audience as it is for Cassie in the moment.”

Amanda Schull and Aaron Stanfield SOURCE: Syfy

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For decades, horror movies like “When a Stranger Calls” and “Scream” have played off the twist that the killer has been in the house all along. Now, “Monkeys” has seemingly updated that with the twist that the killer is inside Cassie. “The killer is literally inside,” she laughs.

Schull continues: “There have been lots of theories, and I’ve seen some people call it on social media. In the last week, people have been sending me theories on social media that Cole and Cassie conceived The Witness. So, I just haven’t responded to anyone on social media, because I didn’t want to ruin it. You don’t really want to know!”

Another treat of the “Memory of Tomorrow” episode was watching some rare moments of peace, via the 1959 Christmas storyline that had Cole and Cassie seemingly ready to live happily ever after.

“Terry was concerned that those Christmas scenes would feel false,” Schull recalls. “But after he saw myself and Aaron work on them a little, he was happy with the results. Aaron and I have lived with these characters under our skin for so long that we know how they would behave. Even though they’ve finally come up for air, they are still themselves under everything. It’s a very different existence for them, and Aaron and I loved shooting the ’50s stuff. Yes, I want Cassie to be that happy — but for Amanda, as an actress? I want to dive back into that ’12 Monkeys’ drama.”

RELATED: ’12 Monkeys’: Cassie & Cole fans ‘will not be disappointed’ with the end of Season 2

Now that the show has left you with your jaw on the floor, Schull says she can’t wait to get to work on Season 3. “I’m so excited,” she enthuses, thinking back to the show’s on-the-bubble renewal.

“There were some days when it wasn’t looking so good, and that was hard to accept. I love that we’re coming back, I love how the characters are evolving, I love the tone and look of the show. And I just want so much to continue this story — and now, to continue it here with this jumping off point? I am really, really looking forward to going back to work on this horrible, despicable, sad but challenging development.”

“We’re going back to work in October, and as soon as they announced the pick-up Terry and the writing staff went to work,” she laughs. “This development will be horrible for Cassie, but wonderfully challenging for Amanda.”