She once served as nest-maid to Soren's family, but when Marella and Noctus were killed by their son Kludd, and all three owlets went missing, she went with the band on their journey to the Great Ga'Hoole Tree after being reunited with Soren, and served tea at the Great Tree and joined the harp guild.
Mrs. Plithiver was Soren's nest-maid snake. She sensed how Kludd had pushed Soren out of the nest, and tried to get help from Hilda, another nest-maid. The evil young owl said that if she did he would eat her and tried to do so, but Mrs. Plithiver managed to escape Kludd.
Later Soren found Mrs. Plithiver in Kuneer under a tree stump while he was out hunting. She accompanied the band to the Great Ga'Hoole Tree by riding on Soren's back while he flew.
Mrs. P. had always sensed something was wrong with Kludd, but did not take it seriously until he tried to eat her. She explained to Soren that Kludd had been jealous of Soren since he hatched out and that he pushed him out of the nest.
At the Great Tree she joined the harp guild, which is one of the guilds for the nest-maid snakes. She accompanied Madame Plonk in her singing, and had a maestro's touch. She was somehow able to sense that Elgantine was alive, and helped Soren hope she was alive as well. She also served as a table for the young owls at mealtimes.
Mrs. P. encourages Pellimore to go with Soren (Books) to the crown of the Great Ga'Hoole Tree (Books) to await the arrival of Coryn with the Ember of Hoole. Pellimore protests but ultimately complies. Mrs. P. then takes over the incubation of Pellimore's eggs. She reminisces on how fast time flew and things changed, as Soren (Books) was once a hatchling, but had at last become a father. Due to her natural sensibilities, she was able to tell that three female owlets were developing within the eggs.
Mrs. P joined the Band as the they journeyed to the Middle Kingdom. Along the way, she lost her tail in the tumblebones. Digger nearly yeeped but she assured him that she's not a rattler and wont her tail again
Mrs. P. does not play as much of a role in the film adaption of the books. She appears to not be blind in the movie, oddly enough. She is seen at the start of the film, constantly watching over and tending to the needs of Soren, Kludd, and Eglantine. When Soren comes back from doing some branching, Mrs. P. is seen trying to help Eglantine yarp her first pellet. When Soren and Gylfie escape from St. Aegolius Academy for Orphaned Owls and meet Twilight and Digger, Twilight brings Mrs. P. to the hollow shared by him and Digger to serve for the band. Soren instantly recognizes her, and insists to Twilight she is not for dinner. As in the books, Mrs. P. and Twilight seem to be quite unfound of each other.
She stays in Twilight's lute when they are flying. When Twilight's lute is stolen by crows, Digger is very thankful, but then he and the others remember Mrs. P. is in there, and they rescue her from the pests. When they reach the Echidna, he names Mrs. P. the heart of the family.
Later when Allomere returns from his recon mission, Mrs. P. goes to the two owlets he brought back. She recognized one of the owlets as Eglantine and called for Soren. Then after the Guardians set out, the scene changes to Soren sitting by a moon-blinked Eglantine. Mrs. Plithver is seen curled on top of the nest looking down at her. When Soren says he wants to trade places with her sister, she makes a worried remark and welcomes Eglantine after she snaps out of it. Her last appearance is when Soren's mother and father, who were still alive in the movie, watched Soren land. She only stands straight with a happy look, then is not seen again.
Mrs. Plithiver is an elderly nest-maid snake that seems to be a grandmotherly figure to the band. In the film, the Echidna dubs her the heart of the band, soon to be family. She rarely is angered at her loved ones and whenever she "swears," the other owls are deeply stunned. However, she is almost always gentle and loving to the owls of the great tree, and often gives them advice or guidance whenever they are at a loss.
She is also extremely perceptive as she noticed right away that Kludd had a dark side.
She appears to have eyes in the movie, whilst in the books she just had indents. She was likely given eyes to make her appear less scary, while her eyes do seem to look blind.
In the movie credits, she's listed as Mrs. Plithiver, despite only ever being called Mrs. P in the movie.
In The Outcast, she briefly takes over the incubation of Pellimore's eggs. Being as blind snakes are cold-blooded, i.e. do not produce their own body heat, she would not have been able to keep the eggs warm. This is either an oversight by Lasky or the only sensible aid Mrs. P. could provide given the circumstances. It is a touching gesture, but not entirely accurate. However, her decision was obviously more logical than leaving Pellimore's eggs uncovered and unguarded.