Lulu knows that Snow White belongs to Rema, a snobby girl who owns the Wiggins horse farm. When Rema comes home from boarding school, Snow White will be her pony. But Rema is mean and treats Snow White badly.
Pam and Anna, Lulu's Pony Pals, know that Snow White and Lulu belong together. The Pony Pals must think up a plan. How will they get Rema to give Snow White up? Can the Pony Pals get Snow White back?
At the start of summer break, Pam, Lulu, and Anna head out to Lake Appamapog for a "last pony ride" with all three girls together, because the start of summer means that Lulu will have to give her pony, Snow White, back to Rema Baxter, who she leases Snow White from, since Rema is back from boarding school in the summer. In addition, Lulu's father, Mr. Sanders is coming back to Wiggins from a wildlife research project in the Amazon jungle, so that means Lulu will be leaving Wiggins to join him on his next project. When they get back from their ride, Lulu's Grandmother Sanders tells them Rema will be back from boarding school the next day, so Snow White will need to be returned as soon as possible to the Baxters' paddock.
When the Pony Pals reach the Baxters' paddock to drop off Snow White, they discover that the stable where Snow White will stay is filthy. They clean the dirty straw, dust, and cobwebs so that Snow White will not have to move into a dirty stall. Lulu says a tearful goodbye to Snow White and leaves her with the Baxters.
Lulu gets a message from her dad say he will be there soon, and she is excited to see him because she hasn't seen him in months. The next morning, her grandmother awakens her to tell her that Snow White has made her way back to the Harley's paddock. This worries Lulu and the Pony Pals because Snow White could get hit by a truck or something if she is walking all the way from the Baxters farm to the Harleys unsupervised.
The Pony Pals ride Pony Pal Trail and back to the Baxters again to drop off Snow White. They arrive just in time to see the Baxter's station wagon pull up and Rema jump out to greet Snow White. Lulu explains that Snow White had escaped and she was returning her. Rema remarks that Lulu is younger than she expected, and that she assumed Lulu was older from her letters, and if she'd known how young Lulu was, she would not have leased her pony to her. Rema laments that Wiggins is really boring for teenagers. Lulu is devastated about the way Rema treats Snow White and her and the Pony Pals. She tries to suggest that Snow White could live at the Harley's paddock and Rema could ride her at any time, so she wouldn't escape again, but Rema laughs in Lulu's face.
That night the Pony Pals are having their last barn sleepover, before Lulu moves. As it turns out, they are also holding a surprise goodbye party for Lulu, will all of their family and friends. All the decorations are periwinkle blue, the Pony Pals' color. Jack and Jill Crandal give Lulu wreaths of straw and daisies, respectively. Ms. Wiggins gives Lulu a journal. Pam gives her The Ultimate Horse Book, her grandmother gives her a fancy hairbrush and comb set, and Anna gives her a portrait she'd painted of Snow White.
During the night of their sleepover, they are awoken by a loud noise. This turns out to be Lulu's dad, Mr. Sanders, back early from South America. When Lulu tells him about how she takes care of Snow White, he tells her how proud he is of how independent and responsible she is. Later, she asks her dad where they are going to live next. He says that he just got approval for a grant to study bears locally, so they can stay in Wiggins.
When Lulu's father goes upstairs to take a nap and her grandmother is busy with her first client of the day, Lulu doesn't know what else to do without a pony so she decides to take a hike. She decides she has to check that Rema is letting Snow White into the paddock during the day. Soon, she spots Rema riding Snow White, but Rema's body isn't in rhythm with Snow White's trot. Lulu can see that neither pony nor rider are having a good time, and she wishes she could give Rema pointers. Rema says to Snow White "I shouldn't have let that kid take care of you. She ruined you for sure."
Lulu decides to leave before she is discovered, and walks as quickly as she can to the Wiggins Estate, where she knows she will find Anna and Pam. When they meet up, Lulu tells them the good news - that she will be staying in Wiggins. However, she also tells them the bad news about how Rema treats Snow White, and that she wants to figure out how to get Snow White back.
The Pony Pals meet at the Off-Main Diner to discuss their ideas. Lulu's father comes with her because he wants to meet some of his neighbors. The Pony Pals explain that Lulu is trying to get Snow White back, and he agrees that as long as Lulu is in Wiggins, she should have a pony. The Pony Pals discuss the situation with Rema and agree to schedule a business meeting with her for the following day.
When they meet with Rema the next day at her house, Rema starts off with "Lucinda Sanders, you have damaged my horse." Rema complains that Snow White is smaller than she used to be. The Pony Pals counter that she is now too tall for a pony, because she has grown a few inches in the last year. They suggest Rema should get a horse. Rema thinks about it, but wonders what she would do with a horse while she is in school during the year. Instead, she thinks about the money she would get from selling her pony, which she could use to go to sleepaway camp with her boarding school friends.
Rema quotes them $2000 as a price, which is way too high. The Pony Pals suggest that she needs an expert, like Reggie Olson, to price a pony. Rema calls Mr. Olson on the phone, and tells Lulu that if she wants to buy Snow White, she should meet her at Mr. Olson's farm at 3:00 the next day, since other people might want to buy her.
When they arrive at Olson's horse farm, Anna notices a familiar car - Tommy Rand's mother's! Tommy Rand is the meanest, bossiest eighth grader they know, and they worry that he will want to buy Snow White. However, he is not interested, but his sister Anita Rand is, and just rode Snow White and plans to buy her. The Pony Pals have to think fast. One of Mr. Olson's policies is that he insists that a potential buyer pays a small deposit and trials the pony first before buying for a week. That means that if Anita buys the pony, Rema won't get the money that day. Meanwhile Mr. Olson suggests Anita try the black Morgan horse, which she ends up preferring. Lulu and her father tell Mr. Baxter that they will pay the agreed-upon price for Snow White, and the Baxters won't have to wait on the money because Lulu already leased Snow White, and doesn't have to trial her. Lulu is thrilled to finally own Snow White for good.
- Anita Rand - Tommy Rand's sister, who wants her own horse or pony
- Mr. Sanders - Lulu's father, who was mentioned in previous books, but appears first in this book