The Goldfish Boy is a middle grade mystery novel by Lisa Thompson, published by Scholastic Inc. in 2017. It was Thompson’s debut novel and garnered critical acclaim. Upon publication, the novel became a national best seller and was shortlisted for the Waterstones Children’s Book Prize. Thompson followed up on her debut novel with her third novella in 2021, The Graveyard Riddle, which follows the lives of characters from The Goldfish Boy. This study guide refers to the 2017 Scholastic Press edition.

Content Warning: The source material features discussions of mental illness, death, grief, kidnapping, and bullying.

Plot Summary

The Goldfish Boy follows protagonist Matthew Corbin, a 12-year-old boy who lives in a suburb outside London with his parents, Sheila and Brian. Matthew is unlike other children his age; he rarely leaves his house and engages in excessive cleaning and washing rituals. Matthew’s unusual behavior stems from his struggle with obsessive-compulsive disorder (OCD), a mental illness he developed as a trauma response to the death of his baby brother, Callum, when he was seven years old.

Having been out of school for weeks due to his severe OCD, Matthew spends most of his time cleaning himself and the spaces around him. When he is not obsessively sanitizing, Matthew likes to observe his neighbors’ daily activities from the window in the spare room of his family home. In addition to watching them, Matthew likes to keep a record of their daily activities in a notebook, where he also notes dates and times at which certain activities occur.

Matthew’s parents are deeply concerned about his mental health. Matthew’s struggle with OCD is at an all-time high, and Sheila and Brian are not sure how to address the situation. Matthew’s cleaning habits are so extreme that Sheila begins providing him with disposable latex gloves in exchange for the promise that he will stop burning his hands with bleach. They attempt to get Matthew into therapy, but their initial visit to Dr. Rhodes does not fare well for any of them.

Matthew feels safest in his bedroom, where he is in control of everything. More importantly, his bedroom is free of germs. To Matthew, germs lead to illness, and illness leads to death. Also in his bedroom is an image of a lion on his wallpaper, a figure he refers to as Wallpaper Lion. Wallpaper Lion, always on the wall, is a reliable and supportive makeshift friend to Matthew, so Matthew spends a lot of time confiding in him.

One day, Matthew, watching from his window, observes Teddy, his neighbor Mr. Charles’s two-year-old grandson, playing alone in the front yard. When Matthew momentarily turns away, Teddy Dawson is kidnapped. From the moment of Teddy’s disappearance, Matthew, the last person to see Teddy, resolves to solve the missing child case and bring Teddy home.

With the help of his two neighbors and classmates, Jake and Melody, Matthew launches a full investigation into the disappearance of Teddy Dawson. Because no one comes forward as a witness to the kidnapping, everyone in the cul-de-sac, save for Matthew and his parents, is a potential suspect.

During his investigation, Matthew carefully considers the lives, personalities, and potential motivations of his neighbors.

Apart from giving him something to do other than clean, the Teddy Dawson case is somewhat triggering for Matthew, as the situation reminds him of losing his own brother, Callum, shortly after he was born. Through the narration, Matthew alludes to his belief that Callum’s death was the direct result of his actions, and that he lives with the guilt of that responsibility every day.

As the last person to see Teddy before he goes missing, the police question Matthew several times. Though they are suspicious of his strange hobbies, his habit of closely observing his neighbors and cataloging their daily goings-on comes in handy several times in the police investigation.

On the night of Teddy’s disappearance, Matthew’s parents host Teddy’s sister, Casey, who refers to Matthew as Goldfish Boy and whom Matthew considers to be evil. In her sleep, Casey tells Matthew that the old lady took Teddy.

About halfway through the novel, Matthew decides that Old Nina, the vicar’s widow who lives at the Rectory, is a prime suspect in Teddy’s disappearance. Old Nina, having lost her own son years ago when he was about Matthew’s age, has a potential motive for kidnapping a child. Though Matthew discovers a few pieces of potential evidence against Nina, he realizes it is baseless when, having been tipped off by Melody’s mother, Claudia, the police search Nina’s house and come up short. Instead of a child, they find a kitten that Nina has been hiding out of fear of getting evicted.

The last suspects with the most potential are Penny and Gordon, Matthew’s middle-aged neighbors who are close to his parents. When Matthew realizes that Penny and Gordon may be suspects, he sneaks over to their house in the night and finds one of Teddy’s toys in the backseat of their car.

Shortly after this discovery, Teddy arrives back on Mr. Charles’s front yard in the early hours of the morning. Matthew is the first person to discover him, which the police find suspicious.

After fending off the police, Matthew returns to Penny and Gordon’s to retrieve the scrap of Wallpaper Lion’s eye that he carries in his pocket for emotional support. While there, he discovers a damning piece of evidence on a window at their house: the sticky handprint of a child.

Penny and Gordon are arrested for kidnapping Teddy. Before leaving, Penny alleges that Casey witnessed the supposed kidnapping and knew where Teddy was all along.

After Teddy’s case is solved, Matthew recommits to therapy. The courage it takes to pursue therapy empowers him to be honest with his parents: Matthew reveals that he is afraid of germs because he has been operating under the assumption that his brother died because Matthew had the chicken pox while Sheila was pregnant with Callum. He vows to try to recover from OCD and heal from his past.

At the end of the novel, Matthew faces his fear and joins his neighbors outside for a barbecue to celebrate Teddy’s homecoming. When Melody—now Matthew’s friend—asks if he is doing okay, Teddy assures her that he will be just fine.