Perdita makes an appearance in the book The Isle of the Lost, in which she and Pongo are part of the council of sidekicks, where Prince Ben (son to Belle and The Beast) is able to communicate with them via a translation device on Ben's ear. She expresses that, while having ninety-nine pups can cause her a lack of sleep, she and Pongo are concerned about the pups' college education. This concern has Ben decide to set up and pass the "Puppy Grant" benefit, allowing financial aid for the Dalmatians.
Perdita is very well mannered, elegant and radiant; a complete foil to Pongo's goofy nature. She is also rather stern, and appears to be a tad more prominent when it comes to disciplining her children, as well as the rascally Pongo.
Despite her well-coordinated nature, Perdita tends to be incredibly worrisome in hectic situations and prefers to avoid oncoming conflict by leaving the scene, as shown when Cruella visits. She is also rather observant, and appears able to sense nearby danger, being the only one to expect Cruella's villainy even before the kidnapping of her children. A complete contrast to the optimistic Pongo, Perdita's worries can often escalate to pessimism, only to be put to rest by the always headstrong and relentless Pongo.
Even so, Perdita is a fierce warrior, and will jump into battle in the situation calls for it. Like Pongo, her primary concerns are her puppies. As such, she has shown to willingly abandon her usual guidelines of self-composure for the sake of her family.
In the original film, Pongo is searching for mates for himself and his pet Roger Radcliffe. Pongo is close to giving up when he spots Perdita and her pet, Anita. Pongo rushes to the park to follow them. Perdita spots Pongo and is seemingly attracted to him, but tries to look as if she doesn't notice him. Perdita and Anita soon leave and Pongo tries a trick to attract their attention. At first, it seems as if it failed, Perdita was mad at Pongo for making her owner, Anita wet. But as Roger and Anita talk more they fall in love. Perdita falls in love with Pongo as well.
Perdita soon becomes pregnant with puppies, but when the family gets a visit from Cruella De Vil she becomes frightened, referring to Cruella as "that devil woman." Perdita hides but is able to hear Cruella's desire for the puppies. Perdita regrets having puppies due to the fact that Cruella wants them. Unfortunately for Perdita, the puppies arrived three weeks later, where it is revealed that she has had fifteen puppies. She is tired afterward but is relieved to hear from Pongo that the puppies are safe thanks to Roger. The puppies grow and are shown watching their favorite show with their parents. Perdita is seen interacting with her various puppies: telling Lucky to get down from the TV, reminding Rolly that they just had dinner, and scolding Patch for his coarse language.
After the puppies are put to bed, Pongo and Perdita go on a walk with their respective owners. During their absence, the puppies were kidnapped by Cruella's henchman Jasper and Horace. Pongo and Perdita realize that neither the humans nor Scotland Yard will find their puppies, and take it upon themselves to rescue their children. They use the twilight bark, a canine gossip chain, to spread the news of their stolen puppies. Later, they receive an answer and learn that their puppies are at Hell Hall, Cruella's former home.
Perdita immediately goes off on a dangerous journey to rescue the puppies alongside Pongo. The winter conditions make the journey tough, but they eventually meet with a sheepdog called the Colonel, who takes them to the puppies. Upon seeing the other puppies alongside their own fifteen, they decide to take them all to London, knowing that Roger and Anita would never turn them out.