This study guide was created using the following version of this book: Rekulak, Jason. Hidden Pictures. Flatiron Books, 2022.

Mallory Quinn is recently out of rehab for heroin addiction and in need of a job. Mallory is referred as a nanny for Caroline and Ted Maxwell by her sponsor Russell. Mallory’s interview goes well, in spite of Ted’s concerns about Mallory’s past. Mallory begins working for the Maxwell family as Teddy’s nanny. Teddy is a five-year-old boy who has an imaginary friend named Anya. Teddy and Mallory bond quickly. Teddy likes to share his artwork with Mallory.

Mallory begins to notice some strange things about Teddy’s drawings. Anya appears in the drawings as a menacing figure. The drawings begin to take a darker turn, with drawings depicting a woman’s body being dragged through the woods as well as a man burying the woman’s body. After Mallory befriends Adrian, the college student who helps with the Maxwell family's lawn, Mallory confides in Adrian about the drawings. Adrian shows interest. Mitzi, the neighbor, is an eccentric woman who reads people’s auras. She tells Mallory about the mysterious disappearance of Annie Barrett. Annie once lived in the cottage where Mallory is staying, and rumors have long persisted that Annie was murdered in the cottage.

Mallory begins to suspect that Annie’s ghost may be Anya. Soon Teddy’s drawings begin to change. The drawings become more sophisticated, depicting the dark scenarios from Teddy’s earlier drawings in more detail. With the help of Adrian and Adrian’s mother Sofia, Mallory researches more about Annie Barrett. When Sofia uncovers a collection of Annie Barrett’s drawings, Mallory and Adrian are struck by how different Annie Barrett’s drawing style is from Teddy’s drawings. While Caroline and Ted continue to deny that anything strange or supernatural is at play, Mallory begins to suspect that Anya may be possessing Teddy in order to complete the drawings.

Mitzi helps Mallory by performing a séance during which an unusual sequence of letters is revealed. When Mitzi suspects that Mallory is doing something to move the planchette on the Ouija board during the séance, Mitzi shuts it down and leaves Mallory.

As Mallory continues to figure out what is behind the drawings, the Maxwells grow frustrated with Mallory. After Mallory is exposed for lying to Adrian about her past, Mallory finds herself waking up to see that she has drawn pictures all over the walls in the Maxwell home. Mallory tries to apologize to Adrian for lying. While Adrian is hurt over Mallory’s lies, Adrian believes that Mallory is telling the truth about the drawings because Anya has made Adrian draw as well.

After Mitzi is found dead under suspicious circumstances, Mallory decides to confront Caroline and Ted. When Mallory suggests that Caroline and Ted kidnapped Teddy, Caroline makes a plan to kill Mallory and make it look like an overdose. Ted comes to Mallory’s rescue, but Caroline shoots and kills Ted in the process. Mallory flees from Caroline with Teddy. As Caroline hunts Mallory and Teddy down, the ghost of Teddy’s mother kills Caroline and saves Mallory and Teddy.