Alyssa is a 16-year-old high school junior living in California. She usually relies on her strong moral compass and desires to assist those less fortunate. When the regional water supply suddenly cuts off and her parents go missing, she assumes responsibility for her younger brother. She must adapt her previously charitable mindset to ensure her family's survival in a rapidly worsening society.

Kelton is a high school junior whose family identifies as preppers, stocking their home with weapons and extensive survival supplies. He harbors a long-standing crush on his neighbor Alyssa, which motivates him to step outside his family's strict isolationist policies to assist her. He attempts to balance his father's ruthless survival tactics with his own conscience.

Jacqui is a 19-year-old who lives on her own and squats in empty houses along the coast. She prides herself on her street smarts and considers herself emotionally prepared for the disaster. She agrees to drive the younger teenagers around in an abandoned BMW in exchange for antibiotics to treat an infected cut on her arm.

Garrett is Alyssa's 10-year-old brother. He initially struggles to grasp the severity of the Tap-Out and the concept of delayed gratification. As the disaster worsens and his parents remain missing, he relies entirely on his sister and their neighbors for safety. He experiences intense fear but adapts quickly to the harsh new realities of his environment.

Henry is a teenager who views the Tap-Out primarily as a fantastic business opportunity rather than a tragedy. Left alone while his parents are on vacation, he trades clean bottled water for high-value items like vehicles. He joins Alyssa's group and constantly attempts to manipulate the social dynamics to place himself in a leadership position.

Uncle Basil is Alyssa and Garrett's uncle. He leaves the Morrow household early in the crisis so he does not drain their limited resources. He stays with his girlfriend in a gated community, where he falls ill after drinking contaminated water.

Kelton's father is a strict survivalist who believes in absolute self-reliance. He stocks his home with weapons and booby traps, refusing to share his family's water supply with desperate neighbors. His intense focus on protecting his resources creates friction with his wife and younger son.

Kelton's mother is more community-minded than her husband. She feels uncomfortable with their family's strict isolation and argues that they should share some of their water with neighbors. She steps in to allow Alyssa, Garrett, and Jacqui into their home when they are in danger.

Brady is Kelton's older brother. He lives away from home but is expected to join the family to ride out the disaster. He knows the location of the family's primary bug-out shelter in the woods.

Alyssa and Garrett's father. He attempts to manage the household's water rations early in the crisis. He leaves the house with his wife to search for water desalination machines at the beach and fails to return.

Alyssa and Garrett's mother. She leaves with her husband to secure fresh water for the family, accidentally leaving her children to survive the worsening crisis alone.

Known to her followers as the Water Angel, Charity is an older woman who runs a makeshift commune in the dried-up waterways. She organizes survivors to siphon water from abandoned cars and collect supplies, requiring everyone to work together and share.

Daphne lives in the gated community of Dove Canyon. She becomes severely ill from dysentery after drinking from a contaminated neighborhood water tanker.

A news anchor who realizes the severity of the government's inability to provide water. She abandons her broadcast post and commandeers the station's helicopter to escape to an area with functioning utilities.

Lyla Singh's co-anchor who expresses concern on the air about the deteriorating situation in California.

A social activist who anticipated the water shortage before the Tap-Out officially began. She takes direct action to divert water deliveries to those she feels need them most.

A water transport driver attempting to deliver supplies to critical facilities. He bends the rules to secure a small container of water for his own family before facing an angry mob.

A critical facility manager who defies corporate rules to let his employees shelter their families at the plant. He faces down a violent mob trying to breach the facility's gates.

A National Guard pilot tasked with airlifting drinking water. She struggles with the emotional weight of seeing desperate crowds below while being unable to provide enough aid.

A teenage girl stuck in a makeshift camp. She and her mother are completely unprepared for the crisis, forcing her to consider dangerous and compromising exchanges to secure water.

A teenage girl who secures water by trading sexual favors with an older man at the camp, illustrating the extreme measures people take to survive.

The head of the local homeowners' association who attempts to persuade Kelton's father to pool the neighborhood's resources.

Alyssa's friend who flees with her family to Mexico in the early days of the disaster.