Role in the film
Traveling from Bern, Switzerland to the German colony of New Guinea with her husband and three sons to avoid Napoleon Bonaparte's European conquest, Mother Robinson and her family find themselves caught in a raging thunderstorm when being chased by pirates and trapped in their room of the ship, Titus they were sailing on. Mother and her youngest son, Francis stay behind while her husband, Father and her two elder sons:Fritz and Ernst try to call for help but no one seems to be on board to answer their call until their ship gets caught on the rocks.
In the morning, Mother and Francis manage to get out after Father and their two other sons help break free from their room. They find themselves shipwrecked next to a deserted island, the ship's captain and crew gone, and the animal livestock trapped inside along with the captain's dogs: Duke and Turk.
Mother and her family begin to build a raft made out of the ship's wood and anything else they can find. Then, Mother and her family begin collecting all their belongings including guns and muskets from the captain's cabin and anything else they might need to survive.
Once everyone is on board, they begin to set sail while Francis complains to his father about leaving the dogs behind as Father states they are "too heavy that might sink them." Against Father's wishes, Francis signals the dogs to follow them by swimming despite the strong current. As Father and his two elder sons row while getting closer to shore, the current gets stronger by the minute, making it almost impossible for the dogs to overcome it despite being good swimmers. Mother pleads Father to help them but he is not likely to take any risks. At the very last minute, when hearing the dogs barking helplessly, he has a change of mind and heart and brings them on board the raft without any further incident, thus, proving his theory about sinking them wrong.
Once on shore, Mother calls Francis to rejoin them when she catches him running with the dogs to a Galapagos tortoise. When Father suggests they make camp for the night, Mother suggests they first pray, which they voluntarily do. While Mother provides them with whatever food they have left and Francis feeds the dogs, Father and his two other sons try to pitch a tent on the beach but to no avail while a tiger inconspicuously watches them. After finishing the tent, Father suggests to his two sons to return to the ship tomorrow to begin loading all the animals. Then, Mother screams at the sight of a monitor lizard, so, Father comes to her aid and Fritz tries to shoot it but he can't since the gun's powder was wet.
At night, Mother wakes up to convince Father to sleep as well since he's staying on guard. They start discussing all the problems they've suffered and tried to avoid until it begins to rain, thus, forcing them to stay inside the tent.
The next morning, while Father and the two boys are out bringing the animals from the ship, Mother notices Francis is missing, so, she sends Duke and Turk to find him. They come just time to save Francis and a baby elephant, which Francis caught to be his new pet later named Rocky, from the tiger. After the dogs finish off the tiger, Mother thanks them and scolds Francis for disobeying her but eventually comes to her sense and allows him to Keep the baby elephant.
Later, Mother cleans some of the silverware and other belongings while Father and his three sons, with Rocky's help, are building a treehouse somewhere within the island to keep them safe from the pirates, the same ones that chased them into the storm and whom Father and his two sons tried avoid during the day while bringing the animals from the ship, and some other predators living on the island. When Mother feels uncomfortable with all this, Father reminds her of the situation they are now in. Then, she is brought up by her husband to the treehouse to show her where they'll be sleeping soon but Mother still fears about falling off the edge (same for Francis' sake too). So, Father brings Mother down while Francis catches and adopts a new pet monkey when nearly falling if not for the rope Mother tied around his waist for safety and Ernst holding him. Upset, worried, and scared, Mother instructs Father and the boys to keep Francis on the ground while working on the house and vows not to return until the house is completed; something that Father reluctantly agrees on.
Days (or weeks) later, Father and the boys bring Mother back blindfolded to their new home on a treetop. After removing the blindfold and allowing her to joyfully admire it, Father proceeds with an "old Swiss custom": carrying the bride across the threshold. Mother is shown around her by her husband: the latest running water innovations their two older sons invented and built, the kitchen, the cooler, and all the rooms. When Mother notices a rope in the room, she assumes it's to "ring for the butler" until Father shows her that it is actually used to open the ceiling so as to allow her to look at the stars at night as she once dreamed she would when she and her husband went to Interlaken one summer. However, Mother doesn't like the curtains they brought from the captain's cabin. Nevertheless, she is overwhelmed with joy that she feels she doesn't deserve it until Father comforts her and assures her that he knows "a woman who can fix anything" including the curtains.
A few days later, Mother is heard singing "My Heart Was An Island" as she fixes the curtains in her own design in her room while Father and the boys are out doing their duties. Then, when Mother hears Francis shouting, she comes out of her room to find him and the rest of her family catching and riding an ostrich later named Clementine, which Francis tried to catch first.
Later, Mother sits and watches Father and the boys spending the rest of the day having some fun swinging on vines in a nearby water area. After failing to swing like a monkey while Fritz succeeded and falling into the water, Mother and Father have a small conversation. With all this fun, Father feels this is the kind of life they were probably meant to live in but Mother seems rather concerned about the future especially that of their sons when it comes to the idea of marriage and family. To offer a solution to all that, Father suggests they allow Fritz and Ernst to sail around the coast with the sailboat they've been working on so as to see what they can find and Mother reluctantly agrees since they are choice less. So, Mother, Father, Francis, and Rocky help prepare the sailboat for sailing and wish them luck. Mother also relies on Ernst's knowledge and way of thinking.
A couple of more days have passed and it's Christmas. Mother plays the organ they brought from the ship as Father sings "Oh, Christmas Tree" and Francis enjoys his Christmas gift. Then, Father offers Mother her Christmas gift and comforts her when she starts worrying about their sons as Francis gets ready for bed. When Mother is on the verge of tears, she and Father hear some singing from a distance and decide to check it out. Out there, they notice Fritz and Ernst having returned home safe and sound and with a girl wearing a cabin boy's uniform named Roberta, whom the boys saved from the same pirates that chased them into the storm, riding on a new zebra named Duchess, which they rescued from predators.
Mother dresses Roberta up in a pink dress while Father and the boys discuss a plan on how to defeat the pirates since they are aware of the two boys' actions. Then, Mother comes down with Roberta and starts to play the organ as Father joins in dancing with Roberta. Fritz and Ernst, both in love with Roberta, try to get a chance to dance with her as well. Seeing as to how both sons are fighting over who should dance with Roberta, Mother continues to play and Father decides to continue on dancing with her while Fritz dances with Francis, leaving Ernst completely depressed, partner less, and jealous too.
The next morning, Mother, Francis, and Roberta watch Father and the boys blowing up the ship still stuck on the rocks with gunpowder so as to confuse the pirates about their location. Then, Mother and the rest including Roberta begin to build some traps, snares, entanglements, and other sort of weapons (like coconut bombs).
At night, after Francis, whom along with his family are preparing for the new holiday arranged by Father for tomorrow, has captured the tiger in one of the pit traps, an idea which he has had in mind for the pirates using a piece of meat as bait, Mother and Roberta stays in the treehouse while Father, the boys, and the dogs come to see to it. Then, Mother is happy to hear from Francis about getting his tiger.
The next morning, while the pirates led by their leader, Kuala return to the island and begin looking for their prisoner, Mother and the family prepare for the race of their new holiday. As the Roberta and the boys race on their animals, Mother and Father watch them as they begin to hilariously foul up due to the animals' behaviors. When Roberta returns after Duchess has had her unintentionally riding towards the beach, she warns Mother and the family about the pirates having finally arrived on the island. Mother and everyone else gets ready for their battle positions including the hill as their last battle position.
After the pirates are defeated by the false bridge, the crossbows, the pits including the one with the tiger, the traps, the snares, entanglements, gunpowder fuses including the ones on the boulders, Mother and her family throw coconut bombs at them. When the pirates continue climbing up the hill, Father manages to get them running scared and possibly killed by rolling logs. When it seems that they get the upper hand, Kuala begins to talk to the family about a trade between the "boy" (Roberta) and their lives as a diversion while his pirates sneak up on the family on the cliff behind them. Nevertheless, Mother and everyone else are not gullible enough to fall for Kuala's tricks. Then, the family manage to fight off the pirates with their guns and muskets on the cliff when they hear them coming; thanks to Francis' "pirate alarm", while Kuala and some of his pirates sneak up on them.
During the battle, Mother shoots some pirates trying to attack her and just when it seems that all hope is lost for them, cannon shots are heard firing. At first, they think it's the pirates firing on them until they notice that it's actually a British ship commandeered by Roberta's grandfather, Captain Moreland, another one of the pirates' former prisoners held for ransom, firing on the pirates and their ship, thus, leading to Kuala and his pirates' deaths; much to Mother and everyone else's joy and victory.
After the Captain has had a meal, offers to take Ernst to a college in England, and promises to take the family to New Guinea, Mother finally decides to remain on the island as their new home with the family and the animals; much to everyone's astonishment and joy especially Father's, and the Captain notes that Father will likely be recommended as Governor of the new colony.
Mother is last seen waving good-bye with her family including Roberta, who has decided to remain with the family as well to marry Fritz, and wishing luck to Ernst as he travels to England for his education.
- In the original novel, Mother Robinson's real name was actually Elizabeth. However, in the film, it is unknown if her name was in fact Elizabeth too, since her name was never mentioned in the movie.