Kate first appears in her ranch greeting the Seavers and gives Laura and Bob Seaver a hug, wishing that she should be at the wedding. The Seavers asks her to keep an eye on Shadow, Chance, and Sassy, which she did so and the Seavers left Chance, Sassy and Shadow to Kate and will be back for a few weeks.
The next day Kate prepares breakfast for Shadow and Chance. Chance was in the chicken house barking at the chickens and hears the noise, realizing it's breakfast and goes inside the house. Kate gives Shadow his breakfast, but before she could give it to him, Chance suddenly rushes in, attempting to take Shadow's breakfast, Kate manages to hold him down and gives Chance his and accidentally steps Sassy's tail in the process. Kate apologizes to Sassy for stepping on her tail and prepares her breakfast. But Chance eats her breakfast too despite Sassy's protest.
Kate then calls the Seavers and asks to call Peter that Shadow wants to talk to him and he did. She then goes to her ranch and writes a note to his neighbor friend Frank to keep an eye on Shadow, Chance, and Sassy while she goes to for a horse riding. Unfortunately Chance, Shadow, and Sassy left the ranch for back home worrying about the Seavers.
Sometime later after they left, Frank arrives and begins calling Shadow, Chance, and Sassy, but they are nowhere to be found and he goes to Kate's ranch and finds half of Kate's note left for him. With the shortened message, he thinks that Kate has taken them with her and then goes to feed her animals.
Days passed, Kate returns from her horse riding and she calls Shadow, Chance and Sassy, unknown to her they already left for home and Frank greets her. He asks her how's the horse riding and she replies that it's fine and Frank asks if she took Shadow, Chance, and Sassy and she replies that she did not and can't take them on a horse ride and he claims that the note says she taken them with her. Kate realizes that Shadow, Chance, and Sassy have run away and contacted the forest rangers. The forest ranger then warns her that the Sierras have got bears, mountain lions and other animals that could pose lethal threats to domesticated animals. Kate then asks the forest rangers if anyone else in the park she can call and they tell her that they will alert the other authorities. Frank tells that she has done everything she can to find them. After replying, "Not everything.", she contacts the Seavers and sadly informs them of the pets' disappearance.
Kate was not seen for the rest of the film afterward, it's assumed that she learned that Shadow, Chance, and Sassy are already home. Kate did not appear in the sequel, it's possible that she's still living in her ranch and still friends with the Seavers.