This article contains SPOILERS for Bird Box.

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Fans are calling for a sequel to its ending lends itself to a Bird Box sequel.

Written by Eric Heisserer (Arrival) and directed by Susanne Bier (The Night Manager), Bird Box takes place in a world that's attacked by mysterious creatures that cause people to either commit suicide upon looking at them or go insane and try to get others to look at the monsters. Bullock stars in the film as Malorie Hayes, an artist who's pregnant - and not exactly happy about it - when the creatures attack, and takes refuge at a house with several others shortly after the creatures make their way to the U.S. The movie jump backs and forth between this plotline and a story thread set five years later, where Malorie and two children (whom she calls Boy and Girl) make their way down a river blindfolded in an attempt to reach a safe haven without being killed by the monsters or their "followers".

Related: Bird Box Director Reveals Where Felix & Lucy Originally Took the Car

By the end of the film, Malorie and the kids are successful in their journey and find their way to the refuge, itself a former school for the blind where most of the population is blind, save for the survivors who find their way there. Malorie, feeling safe at last and ready to do more than survive again, finally names the boy (her son) Tom - after Tom (Trevante Rhodes), the war veteran who fell in love with Malorie and helped care for her and the kids before he sacrificed his life to save them - and the girl Olympia after her mother (Danielle Macdonald), who was among the survivors in the house that Malorie stayed in five years earlier (the same place she met older Tom).

Bird Box Sandra Bullock

If that conclusion sounds pretty self-contained, it's because, well, it is. what happened to the characters Felix and Lucy, but that plot point doesn't really matter in the end). In that sense, it's difficult to argue that a continuation is necessary, much less a great idea.

As for the mysterious creatures in Bird Box: they're fine as is and need no further explanation. Bier's decision to never show the monsters was the right one; as the best horror films have shown in the past, it's almost always better to leave scary creatures to audiences' imagination, where they're bound to be far more terrifying than anything a visual effects artist can come up with. Bird Box makeup designer Andy Bergholtz did, in fact, put together designs for the monsters, but even he's said the movie was better off not including them and leaving the creatures' appearances (which is supposed to vary from person to person, anyway) up in the air.

More than that, the mystery around the monsters ties into Bird Box's themes about parenthood and how raising children can mean preparing them to live in a world full of dangers that even their parents don't really understand. A sequel that attempts to shed more light on the creatures' motivations (and/or how they can be defeated) would risk muddling the simple, but effective idea behind the story here in the first place. Sometimes, a single film really is all that's needed to get the job done.

MORE: Bird Box's Biggest "Mistake" Is Actually Why It's Great

Bird Box is now available for streaming through Netflix.