Aunt Vi leads Maya and Payton to a pool in the Sweetwater River for a camp baptism. After hesitating, Maya jumps into the cold water and finds herself laughing. She washes herself thoroughly with shampoo, feeling simultaneously dirtier and cleaner than ever before. While drying off on the riverbank, Aunt Vi explains that Payton is teased by his three older brothers at home and excels at riding, the one thing in which he outshines them.

Aunt Vi suggests that Grandmother Menetti’s overprotective behavior was a form of love, and this idea surprises Maya, who describes how her grandmother blamed Ellie for the death of Gregory and forbade her from saying her mother’s name. Aunt Vi explains that after Maya’s other grandmother died when Ellie was a baby, Vi came home from teaching art history to help her brother Moose raise Ellie.

Aunt Vi reveals that they will see a wild horse band tomorrow and will meet Artemisia, the horse from Maya’s photograph. Aunt Vi recounts how she bought Artemisia at an auction and trained her for three years. When Ellie visited at age four, she and the horse formed a deep connection. Later that summer, during a pack trip, a careless photographer allowed Artemisia to wander off, and a stallion lured her back into the wild. Aunt Vi recently spotted Artemisia with a new foal named Klee. She explains that she names the wild horses after famous artists because they appear like brushstrokes of color on the landscape’s canvas.

When Payton returns with a snake but releases it unharmed, Aunt Vi notes his improved behavior. Maya confesses that she unlatched Wilson’s gate on purpose. Aunt Vi thanks her for admitting the truth and admits that she deliberately pushed Maya hard during the lesson. She praises Maya, telling her that she is a natural rider, just like a true Limner.

Artemisia, the lead mare, guides her band toward a water hole in the gulch. Her foal, Klee, prances beside her while Georgia, another mare, supervises him. As they descend toward the water, Artemisia notices three figures watching from a hillside. The stallion, Sargent, whinnies to assess the threat, but Artemisia reassures him. After determining the humans are not dangerous, Sargent follows the band.

Artemisia notices Wyeth, a two-year-old colt, is not with them. He calls from the foothills and tries to approach, but Sargent aggressively drives him away with threatening postures and an angry squeal. Though Wyeth is Georgia’s son and has been with the band since birth, it is time for him to leave his natal family and join a bachelor band. Artemisia and the other mares do not interfere with Sargent’s fierce rejection. After repeated rebuffs, Wyeth hangs his head and disappears over a hill, alone for the first time and forced to choose his own path.

At the water hole, the horses drink and roll. Artemisia drapes her neck over Klee, reassuring herself that he is not yet ready to face the same exile.

After breakfast, Aunt Vi, Maya, and Payton trailer their horses south along the Continental Divide to an overlook of the Great Divide Basin. The vast landscape stretches before them, featuring the Honeycomb Buttes, Continental Peak, and Oregon Buttes. As they ride, Maya witnesses mirages and watches a pronghorn herd bolt across the panorama.

They dismount and tie their horses near Oregon Gulch to wait for the wild horses. Maya asks about ghost horses, recalling something her mother told her about “painting” the wind. When Aunt Vi spots Sargent’s band approaching the water hole, Maya views Artemisia through binoculars for the first time and feels an immediate connection. The mare appears strong and regal despite her matted mane and dirt-crusted coat. Maya is charmed by Klee, the playful foal. They also spot Wyeth alone on a hill. Aunt Vi explains that the stallion has driven him from the band so he can join bachelor stallions and eventually start his own family. Payton heads back to the trailer early.

Maya watches Artemisia mothering Klee and feels jealous. When she asks how Artemisia became lead mare, Aunt Vi explains that leadership comes from confidence and knowledge of the land, not size or age. Maya compares Aunt Vi to a lead mare. As Aunt Vi grows emotional and begins to express how Ellie filled a void in her heart, Payton runs back, leading all three horses, and warns of a helicopter in the canyon.

They watch as the helicopter drives the panicked wild horses into a government roundup trap. Aunt Vi explains the complex politics of wild horse “gathers” like this one, describing the pressure from ranchers and the debates over whether mustangs are a native species. Payton adds that many captured horses are sold for slaughter. After the roundup, Aunt Vi identifies Sargent’s band in the holding pen, including Wyeth, whom she surmises must have been trailing them. When Maya asks about Artemisia and Klee, Aunt Vi confirms that they are missing from the gather. Though Maya is relieved, Aunt Vi warns that without their stallion’s protection, the mare and foal are now dangerously vulnerable. They return to camp in silence, and Maya is determined to find and save them.

Several days after the government gather, Artemisia and Klee wander north of the gulch toward the Sweetwater River. During the roundup, Artemisia’s instincts told her that Klee could not survive the panicked stampede, so she led him away from it.

At dusk, Artemisia smells a mountain lion stalking them. She remembers once watching a mountain lion kill a pronghorn by hiding downwind, waiting patiently, then leaping 20 feet onto its victim’s back and delivering a fatal bite. As the predator’s scent intensifies, Artemisia spots the crouching cat. When it springs to attack, she rears and drives it off with her hooves. The surprised mountain lion flees, but Artemisia knows it is hungry and will continue to stalk them. She urgently leads Klee away from the area.

Moose and Uncle Fig arrive at camp with Golly. While Payton takes the dog to see a beaver dam, Maya excitedly tells Moose everything that has happened, including that Artemisia and Klee are missing. Aunt Vi confirms that Maya’s stories are now truthful, and Moose declares that they must get the horses back.

A severe rainstorm forces the family inside the kitchen tent for two days. To escape the monotony, Maya helps Aunt Vi organize her messy office tent. While unpacking art books, Maya notices that the artists’ names match the wild horses and sees a photograph of a black stallion. Aunt Vi identifies him as Remington, a patient stallion who previously tried to steal Artemisia from Sargent. She hopes that Remington might find and protect Artemisia now.

Maya discovers old family photographs, including one of her mother riding Artemisia bareback, using only a rope loop. Moose explains that the technique is called a Comanche Coil, as it has been used by Plains Indigenous people to ride without a saddle or reins. He reveals that in the photograph, Ellie was waving at baby Maya, who had been giggling at a hawk overhead. Maya is moved to realize that she was the source of her mother’s joy in that moment.

After the rain stops, the family searches for Artemisia and Klee for several weeks without success. Payton stops accompanying them, and eventually, Aunt Vi tells Maya they need to pause the searches so that she can work and the horses can rest. Maya refuses to give up hope, whispering promises to her toy stallion each night that she is coming for Artemisia.