Regan Abbott

Regan grows up on an isolated New York farm, where the family talks in sign language and walks on sand paths. She carries a guilt nobody says out loud: her little brother Beau died after switching on a noisy toy. Regan had handed the toy back to him, and he sneaked the batteries.

Her father, Lee, spends his nights trying to build a device that will let her hear. She thinks he only wants to fix his daughter and never forgave her. When the attack reaches the farm, Regan finds out that the device's high whine hurts the creature. Lee, wounded, signs that he always loved her and offers himself as bait. Earlier, she and Marcus had climbed a corn silo to light a signal fire. Marcus fell in, Regan jumped after him, and the device, switched on by accident, made the creature back off. Regan heads home with what she learned.

More than a year later, Regan has turned her cochlear implant into a weapon: it sends the high whine through a handheld microphone. With no home, she sets out with her mother Evelyn, her brother Marcus and the baby. The family reaches an old foundry and finds Emmett, a friend who lost everyone and lives locked in a bunker.

Marcus hears a song looping on a radio station, and Regan reads the message: there are survivors on an island, and from there the signal can reach the whole world. She goes alone. Emmett saves her from an attack and finally decides to come along. On the island, Regan broadcasts the signal, incapacitates a creature and kills it with a metal rod. Before that, at the marina, the two are ambushed by looters, and Emmett draws the creatures in, who kill the men. One of them drowns, and Regan realizes they can't swim. They escape by boat to the island. Then she leaves the implant wired to the station's microphone so other survivors can use the signal.

Millicent Simmonds is deaf in real life and worked with an American Sign Language coach. In Part II her role grows and becomes the film's backbone.