Not all successful movies need to be franchises. Most really shouldn’t be. That’s not how Hollywood works, of course, but it’s worth repeating. Because in the case of “ A Quiet Place,” now on its third movie with a prequel about a few new characters in New York on the first day of the invasion, the thrill of that fresh idea has waned. And when that happens, what are we left with?

There were certainly many questions about the how and the why of the killing monsters with hypersensitive hearing. The internet is full of logic questions and holes if you’re curious. But the beauty of “A Quiet Place” was the silly mystery. We were just dropped into this apocalyptic world with a very simple but challenging rule: If you make a noise, you die. Got it. Scarcity of information worked in its favor as we got to know this family just trying to survive (and deliver a baby quietly!) Its sequel worked mostly because it smartly chose to continue that same journey, picking up exactly where we had left off.

“ A Quiet Place: Day One,” directed and co-written by Michael Sarnoski (sharing a credit with John Krasinski), shifts focus from the Abbott family to a new character, Sam ( Lupita Nyong’o ), who is dying of cancer. She is bitter, sarcastic and mean. And taking the “save the cat” idea to its literal extreme, Sam does have one friend: A cat named Frodo. This seems like an unnecessary crutch, simply because if anyone is going to make a hostile character a compelling hero, it’s Nyong’o. Both she and Joseph Quinn, playing a British law student named Eric, have deeply expressive eyes that make dialogue almost unnecessary. But without a newborn in the mix, the cat adds an extra element of chaos by surviving for more than 3 minutes.

Sarnoski, who was behind the Nicolas Cage thriller “Pig,” makes the bold decision to not dwell on answering questions about the monsters. In fact, he barely addresses how everyone figures out that they need to be quiet. One moment, people are being devoured in the streets of New York and several later there’s a band of survivors pushing their fingers to their lips. Perhaps this was smart: There’s only so much an audience will tolerate watching characters bewildered about something they already know. But it might have been a little interesting to watch someone figure it out, or, like try to persuade a toddler to buy into it.

Besides a distracting attempt to connect this film to “Part II” through Djimon Hounsou, the story itself is quite contained to Sam and Eric, a stranger who kind of attaches himself to her and Frodo. She has one goal: To survive long enough to get to her favorite pizza place in Harlem.

There is something compelling about the idea of what a terminal person might do on the first day of the apocalypse, and Nyong’o is powerful and heartbreaking on this quest for the perfect slice. There’s a beauty in the simplicity and insanity of it. What Eric is doing there, however, is anyone’s guess. He’s a little too underwritten to make much sense of.

Also, there are competing forces at play, with “Day One” wanting to be both a meditative character study and a thrilling horror movie that gives us more monsters, more carnage, more jump scares and unsettling memories of 9/11. They never quite mesh, and several choices make it seem like the filmmakers were just trying to shoehorn in excitement without much justification. One of the most exciting sequences that captures the terror of Krasinski’s films is when Eric goes to a pharmacy to try to get meds for Sam. It’s simple, efficient and full of dread and tension because it’s a necessary risk, unlike many of the bigger set pieces that feel more strained.

Ultimately “Day One” could have been set around any old apocalypse. Tethering it to the rules of “A Quiet Place,” a smart premise whose novelty is impossible to recreate let alone build a world upon, just holds it back.

(“A Quiet Place: Day One” contains terror and violent content/bloody images)

‘A QUIET PLACE: DAY ONE’

Rated R. At the AMC Boston Common, South Bay Center, Causeway, Alamo Drafthouse Seaport, Landmark Kendall Square Cinema and suburban theaters.

Grade: B