The story opens in the library, where Sister Bear impatiently waits for Brother Bear to check out a book when she is at the check out desk. He finds a book titled The Case of the Crying Cave, and Sister remarks that it sounds scary, and by contrast, borrows a much more cutesy book. Once they get home, both start to read their books, but Sister looks at her storybook about three little kittens who are fighting about which is the cutest and she gets a little bored with hers, and begins reading with Brother. Brother begins to dramatize the book, and makes a howling noise that freaks out Sister.
When they go to bed that night, Sister begins to picture dark things as spooky, and has trouble sleeping. Brother then makes a wailing noise, which causes her to cry for help. She cries out "Mama, Papa, hurry! Come quick!". Mama and Papa rush into the kids' bedroom, tripping over each other, and Sister falls down on top of them. Mama and Papa try to convince her that there's nothing to be afraid of, but it doesn't do any good at all, and both siblings fight to determine who would sleep with the lights on or off.
The next morning, the Bear family is too tired to do anything due to their lack of sleep. Papa explains that her imagination has been taking control of her and making the dark look spooky. He takes her upstairs to the attic, and she tries not to let her imagination take her over. She soon begins to learn that she was only fooling herself and there was really nothing to be afraid of the dark. Papa proceeds to show her his old night light, telling her that even he was afraid of the dark once, which puts Sister Bear in disbelief.
That evening, she goes back downstairs and decides to finish reading the rest of The Case of the Crying Cave. She gets disappointed when the wailing noise heard in the book turned out to just be the wind, and remarks about this to Brother that night. The story has ended with Brother Bear feeling a little uneasy about the darkness, and deciding that maybe he's had quite enough mysteries for a while.
