In a world recently overtaken by a virus that turns people rabid within 48 hours, Andy Rose, his wife Kay, and their baby Rosie are traveling down a river on a houseboat in rural Australia. Short on food, Kay suggests going ashore and scavenging, but Andy rejects this, arguing it would be safer to remain on the river until they reach their destination, a supposed refuge. The next day, Andy searches an abandoned sailboat and retrieves some supplies, but when Kay ventures out to collect more, she is bitten by a rabid human.

Andy finds Kay trying to bandage the bite wound and insists on taking her to a hospital since she would bleed out long before succumbing to the virus. The Rose family disembarks, restarts an abandoned car, and sets out toward what their map indicates is a large town, but they swerve to avoid an Aboriginal man standing in the road and crash. Kay is impaled and Andy faints. By the time he wakes, Kay has already turned and bites him. Andy removes Rosie from the car and prepares to defend himself against the man, who is also turned, but a girl named Thoomi appears and reveals that the man is her father, Willie Bell. Thoomi has been hiding Willie from her mother, Josie, and the rest of her community because the Aboriginals are systematically burning the infected. She believes her father can be cured by having a shaman restore his soul.

Andy reaches the town, but it is much smaller than expected and deserted apart from Etta, a schoolteacher who takes care of him and Rosie for the night. Etta explains that all of her students and their families, most of them Aboriginals, have discarded modern trappings and gone back to the old ways; she warns Andy to hide his bite mark. Andy wakes later than planned the next morning after experiencing his first seizure from the virus. When Andy and Rosie leave, Etta shows them a picture of Thoomi and her parents and tells Andy to find them and leave Rosie in their care.