Role in the film
Traveling from Bern, Switzerland to the German colony of New Guinea to avoid Napoleon Bonaparte's European conquest, Father and his 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. Father and his sons 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, Father and his two elder sons, Fritz and Ernst, help break free from their room to allow his wife, Mother, and youngest son, Francis to get out as well. 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.
Father and his family begin to build a raft made out of the ship's wood and anything else they can find. Then, Father and his family begin collecting all their belongings including guns and muskets from the captain's cabin and anything else they might need to survive. When Francis starts loading some of the animals from the ship including the dogs, Father clearly explains that they won't sail to shore with the animals until everyone is safe, so, he begins to unload the animals to help them the next day; much to Francis' chagrin.
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, Father calls Francis to rejoin them when he 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 up 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. When Father hears Mother screaming at the sight of a monitor lizard, he comes to her aid and Fritz tries to shoot it but he can't since the gun's powder was wet.
At night, Father stays on guard while the family sleeps. Then, when Mother wakes up to convince him to sleep as well, 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, Father and his two sons are on the ship preparing the animals for the loading on their raft until Ernst spots a ship heading their way. Through a telescope, Father recognizes it as the same pirate ship that chased them into the storm in the first place. The three try to fight back with a cannon when the pirates led by Kuala begin to shoot at them until Father manages to scare them away with a quarantine flag (meaning and warning there's Black Death aboard), something he read and learned about at some point. As Father and his sons sail with the animals, who prove to be a bit too heavy to carry and pull, they come across some sharks trying to attack the animals. So, Father and Fritz use their guns to shoot at them while Ernst hits them with a stick. When they've finally killed and scared off the sharks, they encounter a sea turtle passing by. Ernst, using his head, lassos a rope to it, which helps the three with the pulling of the animals faster than expected.
Later, after Francis finds and adopts a baby elephant he later names Rocky and are both saved from the tiger by the dogs, Father and his three sons, with Rocky's help, are building a treehouse somewhere within the island to keep them safe from the pirates 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, he brings her up 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. Father begins to show her around: 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, Father works on the forgery and metal while Fritz and Ernst build a sailboat out of a log. Father and his sons discuss their location being an island or not and about sailing around the island to see if they could find either a village, a place where ships come in, or anything else that might help the family leave the island despite Mother's worries. Then, Father and the boys notice some ostriches passing by until they also witness Francis trying to catch and adopt one of them later named Clementine. Father and the boys go after Francis and the ostrich and catch it while tending to Francis too. To get the large bird trained a bit first, Father allows Ernst to ride it first.
Later, Father and the boys spend the rest of the day having some fun swinging on vines in a nearby water area while Mother sits and watches them. After failing to swing like a monkey while Fritz succeeded and falling into the water, Father and Mother 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 so as to see what they can find and Mother reluctantly agrees since they are choiceless. So, Father, Mother, Francis, and Rocky help prepare the sailboat for sailing and wish them luck. Father also relies on Fritz's judgment and good sense, thus, leaving Fritz responsible.
A couple of more days have passed and it's Christmas. Father sings "Oh, Christmas Tree" as Mother plays the organ they brought from the ship 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.
Despite the good deed the boys had done, Father knows that the pirates will return to look for their prisoner for ransom, which is why he decides to get his family ready for battle against the pirates should they ever come back even if it means destroying their ship stuck on the rocks to confuse the pirates about their location. Later, Father joins in dancing with Roberta, now wearing a pink dress as Mother plays the organ after Mother dressed her up in a pink dress. 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, Father decides to continue on dancing with her while Fritz dances with Francis, leaving Ernst completely depressed, partnerless, and jealous too.
The next morning, Father and the boys manage to blow up the ship with gunpowder. Then, Father and the rest including Roberta begin to build some traps, snares, entanglements, and other sorts of weapons (like coconut bombs). Later, when Father hears Francis shouting about Fritz and Ernst fighting over Roberta while working on one of the traps, he runs and arrives just in time to break up the fight. To forget about all this, Father decides to create a new holiday in New Switzerland (the island's new name) the following day.
At night, after Francis, whom along with his family are preparing for the new holiday 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, Father, the boys, and the dogs come to see to it. Amazed and stunned that the trap worked, Father congratulates Francis and begins to cover the pit trap with his sons while Francis goes back to tell his mother and Roberta.
The next morning, while the pirates led by their leader, Kuala return to the island and begin looking for their prisoner, Father and the family prepare for the race of their new holiday. As the Roberta and the boys race on their animals, Father and Mother 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 Father and the family about the pirates having finally arrived on the island. Father gets everyone 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, and entanglements, Father begins to light up gunpowder fuses to explode on them including the boulders, where they planted gunpowder as well. Then, he and his 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 Father 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, Father and everyone else are not gullible enough to fall for Kuala's tricks. Then, the family manages 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 upon them.
During the battle, Father is wounded on the left arm 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 Father 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.
Father is last seen waving good-bye with his 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, Father Robinson's real name was actually William. However, in the film, it is unknown if his name was in fact William too.