While on a delivery run, Mr. Edwards makes friends with Buffalo Bill (no, not THAT Buffalo Bill, just someone who is so named), an elderly gent who is traveling through southern Minnesota. That night while camping, Bill falls seriously ill and begs Edwards to take care of his "little girl," Blanche.
Only after the man dies, and Edwards pays his last respects, does he meet Blanche. She's as ugly as he is, and no wonder. Blanche, you see, is actually an orangutan.
After making funny faces and getting kissed by the ape, Edwards immediately becomes friends with the animal. She also makes quick pals with Nels, Laura and most of the schoolchildren, though she turns off Rev. Alden. And Mrs. Olesen has also expressed her disgust for Strawberry, who has been on the receiving end of one of those smelly kisses.
While Mr. Edwards tries to contact officials with a Chicago zoo that will take Blanche, she is getting into mischief, and one of her actions nearly ends up costing her her life, thanks to Mrs. Olesen.
At school, Nancy gets frustrated with Blanche, who does not like the brat. When she won't share a ball, Nancy tries to hit the orangutan. In self defense, Blanche attacks her, tearing her dress. As usual, she runs home to mommy crying, and an irate Mrs. Olesen – having heard only Nancy's side of the story and refusing to hear any more testimony – calls the sheriff to demand Blanche be destroyed.
Edwards and the schoolchildren learn that Blanche is living on borrowed time, so – with help from Willie and Edwards – they all devise a plan to fool Mrs. Olesen and Nancy into thinking the sheriff killed Blanche. The plan comes off without a hitch, and all's well that ends well, right?
Mr. Edwards - knowing that Mrs. Olesen and Nancy will have him arrested if the orangutan is seen alive - sends Blanche to live with Laura until the zookeeper arrives. Later on, Jenny is home watching Rose and Blanche when she goes outside to milk the cow. A lantern gets knocked over on the table, starting a fire. Blanche rescues Rose and, alerted by Rose's crying, Jenny is able to run to the house to extinguish the fire before it causes any damage.
Jenny relates her story to Jeb and Jason at school, unknowing that Nancy is eavesdropping. Knowing Blanche is supposed to be dead, Nancy quickly tattles to mommy. Mrs. Olesen orders the sheriff back to finish the job.
The other children - including Nancy's own brother!!! - run the brat off while the sheriff is inside ordering Mr. Edwards to reveal Blanche's whereabouts. Almonzo tells Edwards to tell where the orangutan is and they go to the Wilder homestead.
This time, Blanche hides in a tree, just long enough for the zookeepper to arrive and convince the sheriff and Mrs. Olesen to let Blanche live ... which the nasty Harriet does.
Edwards can't bear to let go of his new friend, but he does.