Per wiki policy, Spoilers Off applies here and all spoilers are unmarked. You Have Been Warned.
As an emotional family drama against an apocalyptic monster takeover, this film has some absolutely heart-wrenching moments.
- At the beginning of the film, the wall covered in hundreds of missing person posters. Each one of these people was someone's parent, child, sibling, friend, whatever...and their loved ones were desperately searching for them, not knowing they had been killed by a monster.
- The death of Beau, the youngest child of the family — a four-year-old who had absolutely no understanding of the gravity of the situation his family was in and only wanted to play with a toy. As his father futilely rushes to save him, his sister and mother are forced to watch a creature swipe him away, with Evelyn having to cover her mouth as she is physically unable to cry aloud.
- The aftermath of Beau's death — more specifically, Regan's guilt, since she gave the toy spaceship back to him after their parents took it away and removed the batteries, which resulted in his death when he re-inserted the batteries behind her back, turned it on and it made a loud noise, attracting the monster that killed him. Regan continues to visit his grave, laying down the toy spaceship at his memorial site. What really hammers it home is seeing her cutting the sound wires to Beau's toy spaceship, all while tearing up with guilt clearly consuming her. It's so bad she's convinced herself her father blames her for Beau's death and thinks that he would abandon her to the monsters if she was truly in danger.
- Evelyn's guilt is also heavy and comes from knowing she could have carried Beau instead of letting him wander at the back of the group, which would have prevented the tragedy.
- Regan trying the hearing aid her father made for her, despite insisting they never work. This one fails as well, and Regan breaks down crying, obviously having still hoped. Her actress, Millicent Simmonds, really sells it, and the fact that she is deaf in real life only makes it hit harder.
- The death of Lee, the father. When he sees his children threatened by one of the creatures with no escape, he does not even hesitate to sacrifice himself for them. The only delay is to finally sign "I love you. I have always loved you," to Regan and Marcus, before screaming to draw the monster to him, facing death without flinching as his children escape.
- Originally, the script only had Lee signing "I love you." It was Millicent Simmonds who suggested the "I have always loved you" addition to John Krasinski. This suggestion moved him to tears, and he could barely keep it together when shooting the scene.
- Evelyn witnessing her husband dying on the TV monitors before breaking down with her children.
- The look of absolute heartbreak on Regan's face when she realizes what her father is about to do to save her and Marcus.
- Lee and Marcus come across the body of an old woman, apparently killed by one of the creatures right in front of her husband. Lee pleads with him to keep quiet, but his face contorts with anguish before he finally howls in rage and despair, effectively committing suicide as a creature cuts him down.
- When the kids light a fire on the top of the silo, they look out and there are no fires elsewhere, implying that everyone else is dead.
- Lee all alone in his basement, silently keying SOS into his radio and getting nothing back but static.
- Lee assuming his wife Evelyn was killed by the creatures after finding blood from going into labor in the bathtub. The look on his face is heartbreaking.
- His face is contorting — just like the old man's did before he screamed. You get the impression that if Lee didn't have Regan and Marcus, and Evelyn hadn't revealed herself seconds later, he would've howled just like the old man.
