Plot
Sightless aliens with sharp hearing and impenetrable armored skin have taken over the planet and killed most of the human population. The Abbott family – father Lee, mother Evelyn, deaf daughter Regan, and sons Marcus and Beau – live on their isolated farm in the middle of a forest in Millbrook, New York, and have survived by taking precautions such as laying sand paths to avoid stepping on crunching leaves and using American Sign Language when communicating.
When the family goes into the nearby town for supplies, Beau finds a toy Space Shuttle, but Lee takes out the batteries and makes Beau leave it behind due to the noise it would make if powered on. As they are getting ready to leave, Regan returns the toy to Beau without its batteries, but Beau takes the batteries without anyone noticing. While walking back home, Beau activates the toy, which starts making noise. Almost immediately, Beau is killed by a nearby alien before Lee can reach him. Regan suffers terrible guilt after Beau's death. She hides her feelings of guilt from her parents, although Marcus is aware of them.
Over a year after Beau's death, Evelyn is pregnant with a fourth child. Lee is trying to build a working hearing aid for Regan, but can't master the electronics; the attempt causes a high-pitched noise, but does not improve hearing. Marcus reluctantly goes fishing with Lee while Regan, upset that she cannot go, visits Beau's grave. While the rest of the family is away, Evelyn goes into labor. While heading to the basement, she accidentally steps on an upright nail and drops a photo frame, alerting a nearby alien which enters the house. Struggling to stay silent amidst the pain, Evelyn flips a switch in the basement, turning the surrounding lights around the house red. The alien enters the basement soon after, but Evelyn distracts it by setting off an egg timer and escapes upstairs. Upon returning to the farm and seeing the red lights, Lee instructs Marcus to lure the alien out of the house by lighting off fireworks, allowing Evelyn to safely give birth to her baby.
Regan, seeing the fireworks, runs back to the house. Lee enters the house armed with a shotgun and finds the baby and Evelyn, then brings them into a hiding spot under the floor in the barn outside. The baby cries, and a creature enters the barn. The alien fails to find the source of the noise, but breaks some water pipes. Evelyn wakes up in the flooded hideout with the alien still inside and hides behind the falling water to mask her and the baby's sound.
Marcus and Regan climb to the top of a corn silo and light a signal fire to alert their father, but after the fire dies, Regan wants to leave. In trying to stop her, Marcus falls into the silo, and a segment of the roof that he fell through falls in after him. Regan jumps in after him and guides him on to the fallen roof segment, but then gets sucked into the corn, disappearing from sight. Marcus reaches in and, feeling Regan's hand, is able to pull her out. However, hearing the commotion, the alien, which is hunting for Evelyn, runs towards the silo and attacks Regan and Marcus. Unbeknownst to Regan, as she attempts to use the hearing aid her father was building, she fails to see the alien behind her and the faulty disruptive effect of the hearing aid emitting a high pitched whine, causes the creature to reel in pain and retreat, breaking a hole in the silo which frees the children. Lee finds Regan and Marcus and directs them to his truck when he sees an alien nearby. When the alien attacks him, he is wounded, and Marcus cannot stifle a scream. The alien then attacks the truck, and Lee prepares to distract the alien to save his children. Lee signs to Regan that he has always loved her and proceeds to yell to draw the alien's attention. Marcus and Regan safely coast the truck back to the house.
Reuniting with a grieving Evelyn, they make their way back into the house, followed by an alien. Regan's hearing aid again misfires, causing the alien to react and Regan, now realizing its reaction to the high-pitched noise from her implant, places it on a microphone which amplifies the noise. The alien screeches in pain and involuntarily exposes the vulnerable tissue beneath the armor plating on its head, allowing Evelyn to kill it with Lee's pump shotgun. Armed with high-pitched sound as new weapon, the family prepares to defend themselves from the approaching pack of aliens who heard the shot; in the final scene, Evelyn is seen defiantly racking the shotgun, putting a live shell in the chamber.
