Amelia rips up the book and disposes of it. She attributes the events to Sam's behaviour, but he blames the Babadook. Soon after, strange events occur: doors open and close mysteriously by themselves, strange sounds are heard and Amelia finds glass shards in her food. Sam's persistence about the Babadook leads Amelia to often have sleepless nights as she tries to comfort him. Amelia is disturbed by the book and its mysterious appearance, while Sam becomes convinced that the Babadook is real. It describes the titular monster, the Babadook, a tall pale-faced humanoid in a top hat with taloned fingers which torments its victims after they become aware of its existence.
One night, Sam asks his mother to read a pop-up storybook called Mister Babadook. Amelia is forced to pick up her son from school after Sam brings one of the weapons there. Sam begins displaying erratic behaviour: he becomes an insomniac and is preoccupied with an imaginary monster, against which he has built weapons to fight. Her late husband, Oskar, was killed in a car accident that occurred as he drove Amelia to the hospital during labour. Amelia Vanek is a troubled and exhausted widow living in the Australian city of Adelaide, who has brought up her six-year-old son Samuel alone.
