Spoiler alert! We're discussing major details about the ending of "A Quiet Place: Day One" (in theaters now).

“A Quiet Place: Day One” is more than just a monster movie – it’s a journey to the past.

The sci-fi prequel traces the first day of an alien invasion in New York, as cancer-stricken Sam (Lupita Nyong’o) ventures to Harlem with her cat, Frodo, and new companion Eric (Joseph Quinn). There, she finds the burnt-out wreckage of Patsy's, her favorite pizza spot, which she used to frequent as a kid with her musician dad. She also stumbles upon the old jazz club where she watched her father play piano, tearfully reminiscing as she flips through old photos.

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Shortly after, Sam makes the ultimate sacrifice to save her friend. In excruciating pain from her illness, and no longer able to go on, she chooses to distract the monsters so Eric and Frodo can safely board a ferry that’s leaving the city. “Thanks for helping me live again,” she writes, before walking outside listening to music. She unplugs her headphones with a faint smile, and just as a creature appears behind her, the screen cuts to black.

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What is the last song Lupita Nyong'o listens to in 'A Quiet Place: Day One'?

The final song of the movie is “Feeling Good,” a stirring anthem made famous by Nina Simone, who recorded the tune for her 1965 album “I Put a Spell on You.”

“It’s tragic, but it’s also satisfying that Sam is going out on her own terms,” Nyong’o says of the moment. “Nina Simone has an inbuilt melancholy in her voice, and it comes across in that song. It’s in complete contrast to what she's saying – the words are, ‘And I’m feeling good.’ I think it treads that fine line between a cry of grief and euphoria somehow.

“You want the protagonist to have agency and you want her to triumph,” Nyong’o says. The filmmakers asked themselves, “How can this moment be a triumph? But I think the song really sends it to that place.”

Writer-director Michael Sarnoski initially considered ending the film with the more upbeat “New York Groove,” by ‘70s glam-rock band Hello. But “it was a little on the nose,” Sarnoski says. “I wanted to take something that seemed hopeless and actually make it really joyful. We tried a few songs to see what fit that moment, and Nina Simone just worked really well.”

Does Frodo the cat survive 'A Quiet Place: Day One'?

After seeing the trailer, many movie fans worried that Frodo wouldn’t live through “Day One.” But rest assured, the feline manages to flee New York, thanks to Sam’s bravery. The cat’s name is a clever wink to “The Lord of the Rings” hobbit Frodo, who embarks on a perilous quest across Middle-earth with his best friend Sam.

“Once I landed on Frodo, I knew it had to be that,” Sarnoski says. “It just made sense for a little nod to this journey they’re taking together.”

The kitty was an integral part of the story from early drafts of the script. “I always imagined him as this savvy street cat that Sam found in her younger days in New York and then raised,” he says. “This image of her walking through destroyed New York City with a cat just seemed perfect. Also, knowing that a cat would be one of the few animals that might have a shot at surviving in the ‘Quiet Place’ world because they can stalk and sneak around. I don’t think a dog would do so great.”

Will there be a sequel to 'A Quiet Place: Day One'?

“Day One” is light on references to the first two “Quiet Place” movies, released in 2018 and 2021. But there is one supporting character who bridges the different timelines: Henri (Djimon Hounsou), who helps Sam when the aliens first strike and later escapes on the ferry.

“Henri’s character is a nod to the second movie because he’s the one who tells the story of New York on Day 1,” Sarnoski says. “I knew he was there (that day), so I liked the idea of using him to connect to the other films.“

Like its predecessors, “Day One” is shaping up as a big box-office success, which could mean sequels down the line. Sarnoski is open to returning after taking the reins from John Krasinski, who directed the first two films.

“One of the great things about the ‘Quiet Place’ universe is that because the idea is so fundamental and relatable, you can really explore any human story you want in it,” Sarnoski says. “I’m very curious to see what happens to Eric and Frodo, and I think there’s a lot that Henri goes through between this movie and (‘A Quiet Place Part II’) that you could explore. There are endless narratives. As long as it’s a novel and engrossing character story, you can do whatever you want.”