In the beginning of the movie, the main character, Malorie is in the car with her sister driving home from the hospital and her sister flips the car and dies because she was possessed by the supernatural entity in the sky that makes people go insane and kill themselves. Luckily Malorie survived the crash.
Malorie wants to save her children and get them as far away from whatever apocalyptic activity is happening in their town. Thus taking them down the river.
Care (for her children)