"The Strain" heads into its fourth and final season with a mandate to wrap up its decidedly different vampire tale — no sparkly hunks, just horrifying monsters — but executive producer Carlton Cuse has another goal in mind. One that involves the youngest regular character on the series, Zack Goodweather (Max Charles).

"Zack is, hopefully, one of the evillest child characters in the history of television," said Cuse. "Who better to mentor him than a giant, parasitic, vampiric creature?"

Based on the book trilogy by executive producers Guillermo del Toro and Chuck Hogan, "The Strain" (Sunday, 10 p.m., FX) centers on vampire The Master and his plan to subjugate the world. All is going nicely for him as Season 4 begins, what with Zack setting off a nuclear bomb that triggered a global apocalypse at the end of Season 3.

The story picks up nine months later. Nuclear winter has fallen, and the vampires, aka the Strigoi, have established a totalitarian regime. Most remaining humans are cooperating with the monsters for fear of their lives.

The good guys are still trying to take down The Master, and Dr. Ephraim "Eph" Goodweather is still trying to save his son, Zack. At this point, however, you've got to wonder if Zack is worth saving. He's now The Master's willing disciple.

I mean, Zack has been annoying from Day 1. His mother was turned into a vampire early in the first season, and he's been a brat while his father tried to protect him from her and the other vampires.

And he did, after all, knowingly set off a nuclear bomb.

"I guess that's the ultimate question for that character — does what he did have some deeper resonance and effect? Is he moved or has been changed by that event? And, ultimately, where is that going to lead him?" said Cuse. "As bad as he is, is there still some shred of humanity left inside of him?"

He wasn't giving away any details about what's to come in this final season, except to promise that "Strain" fans won't be left hanging.

"You get to find out what the ultimate fate of each of those characters is," Cuse said, adding that some of the answers will be "very surprising."

He's has some experience wrapping up long-running series, first with "Lost" and then with "Bates Motel." And, hopefully, he's learned something along the way.

That "Lost" finale remains one of the most disappointing endings in TV history; "Bates Motel" worked far better.

Cuse, del Toro and Hogan agreed it was best to wrap up "The Strain" in one last, 10-episode season.

"And it's kind of great because there's no more stalling around," Cuse said. "Everything is pretty definitive this season. I shouldn't even say 'pretty' — it's very definitive this season."

The series remains on the same trajectory it was when it launched.

"Our characters may be down, and they may be living in nuclear winter, and they may no longer be at the top of the food chain, but they are still determined to defeat the forces of evil," Cuse said. "It's a challenge to know how to end a show well, but I think you ultimately have to really rely on your gut and your heart and really think about what is it that the audience is expecting."

But they're not worried about the expectations of those who read the "Strain" book trilogy.

"The show is its own animal, and it has its own narrative journey," Cuse said. "And so I don't think you can watch this final season of the show and think you know what's going to happen to any of the characters. I mean, all bets are off."