Missis is Pongo's mate. At the start of the book she is pregnant. Later she has fifteen puppies. She cannot feed them all, so Perdita was selected as a foster mother. The Nannies kept Missis from Perdita and the puppies, fearing she'd attack them. However Pongo proved them wrong by letting Missis and the puppies meet the other pups and Perdita. Soon her puppies get their spots, but only four are named specifically. (Cadpig, Patch, Lucky and Roly Poly.) When the puppies are kidnapped by Cruella de Vil, Missis and Pongo run away to find them. Missis is the dimmer of the two, however is smart about many other things. She is overjoyed to find the puppies, and grows close to the other puppies, thinking of herself as their mother. They escape Hill Hall with all ninety-seven puppies, and make the rough journey back to London. They had to roll in the soot to disguise themselves from Cruella, Jasper Badun and Saul Badun . When they got to their house, Missis and Pongo confused the Dearlys, but managed to get inside and reveal themselves Dalmatians. They went to live at Hill Hall.
It is revealed she can tell time but has trouble telling which hand is which. She and Pongo are the first to wake up. She and him try to wake up the Dearlys and cats to no avail. Missis and Pongo try to get to the Sheepdog only to find out he has had the same problems. Cadpig contacts them, explaining about swooshing and telepathy. Missis leads a swooshing class to find out Roly Poly ran into a hedge. She leads the dalmatians to London. She tries to help Cadpig as best she can but gets worried about Roly Poly, who vanished. She sits next to Pongo on the tractor and thinks Cruella is responsible for the sleep. When Sirius appears she worries for him but goes along with Pongo to refuse his offer. When they find Roly Poly she insists on finding out where he's been. When they get home she runs to her basket and falls asleep almost instantly.
- Unlike Pongo, Missis cannot count, read, or tell left from right.
- In Disney's adaptations of the book, Missis and Perdita are combined into a single character.