Summer is here, which means it's time to jump back into the world of causality, time loops, and Primaries again! 12 Monkeys' fourth and final season has a lot riding on it, what with the fate of the world resting in Cassie (Amanda Schull) and Cole's (Aaron Stanford) hands and all.

When Season 3 closed, their son Athan (James Callis) had just been murdered by Olivia (Alisen Down), who in turn took up his mantle as The Witness, revealing herself to be the true villain behind the scheme of the Red Forest all along.

MIND. BLOWN.

With no one left to stand in the way of Olivia's plans to destroy time and The Army of the 12 Monkeys at their door, Cassie, Cole, Jones (Barbara Sukowa), Deacon (Todd Stashwick), Hannah (Brooke Williams) and the Daughters' chances of survival are looking pretty slim. TV Guide talked with showrunner Terry Matalas about how the team will get out of this latest bind, plus what's on tap for the final season.

12 Monkeys Mega Buzz: Who Is Getting Killed Off in the Final Season?

Did you always know how you wanted this story to end, or was it something that took shape over the course of the last three seasons?
Terry Matalas: I knew kind of what the last few scenes would be from the beginning, but about at the cliffhanger of Season 2 was the realization that this was the midpoint and we needed to figure out everything. So at the top of Season 3, in that episode there's actually a scene from Season 4 in it. So we needed to know everything, so we broke out 20 episodes of television before we even started writing the first episode of Season 3.

Was it always the plan to make Olivia the Witness?
Matalas: Not always. We talked about it in Season 1 and then in Season 2 it started to make sense that we were watching the origin story of the villain. Then when we had the twist that Cassie was pregnant and The Army of the 12 Monkeys believed this child to be The Witness, it seemed obvious to me that that just couldn't be the whole story. I personally wouldn't want to watch a show where the next two seasons were about parents trying to kill their kid or, you know, trying to turn him. So that's where we really started leaning into Olivia and started asking those questions.

I did end up loving Athan though, so is there a chance we will see him again in Season 4?
Matalas:
Possibly. I love James Callis, he's the only person I ever saw for that character. We wrote it for him, I called him in and sat him down and said, "I really want you to do this," and was lucky to get him.

What time periods will we be splintering to this year?
Matalas:
You're going to see the Middle Ages in a big way, you're going to see the Old West, and you're going to see Cassie in some really cute 1960s looks.

Alisen Down, <em>12 Monkeys</em>Alisen Down, 12 Monkeys


Given that Cassie and Cole kind of became the enemy for Jones and her team last year, is there going to be any lingering tension or resentment there?
Matalas:
Yes, certainly at the top of the season. I wouldn't say that all is forgiven by any stretch of the imagination, but they're going to have to come together because they have some big problems ahead.

Where are they both at mentally and emotionally after losing their child?
Matalas:
I think Cole is very much on a drive to get to the end of this and certainly by the end of night one you'll see why. There's an element of destiny to him. He feels connected to getting there. But Cassie, who carried a child and was very much on the drive of saving her son, is a bit more hell-bent on actual revenge. So that's going to divide them as we'll see a bit.

What can you tease about how Cole's mother will fit into this puzzle?
Matalas:
Well, she's an important part of the puzzle, but she's sort of kicked off the mission for Season 4. You'll see how Cole's memories of this story she wrote when he was a child are important to his destiny.

You guys really played with causality versus time loops last year, is that once again a roadblock during this season?
Matalas:
It's all about that in Season 4. I think the reason you see the Ouroboros so predominantly is it's the entire theme of the season. You have to end at the beginning. With time-travel... you have to lean into that and not away, so it's a problem for our heroes, our villain and for the audience I think, ultimately. Some hard choices are going to have to be made.

I haven't forgotten that Aethan told Jennifer (Emily Hampshire) that she was an even better Primary than him. Is she really going to be the key to solving this whole puzzle?
Matalas:
I think your answer will come in night one. She's got to get to the bottom of this mystery in the visions in her head. She's seeing these symbols and the Ouroboros and what does that mean. So it's all connected.

Are Cassie and Cole going to have to grapple with the fact that even if they win, they'll lose each other by rewriting the timeline?
Matalas: It's a great question, and none of them seem to be talking about it. In night two, Cassie will talk about it. She's going to say, "You know, just because we win doesn't mean we win. We lose as well, we lose so much." So that becomes an important part of night two.

12 Monkeys premieres Friday, June 15 at 8/7c on Syfy.