Captain Moreland is first seen lying on the beach of an island tied up along with his granddaughter, Roberta, disguised as a cabin boy named "Bertie", after pirates led by their captain, Kuala took their ship and captured them. Captain Moreland is shocked to see the pirates open a chest that belonged and was given to him by his late first officer.
When Kuala and some of the pirates approach them, Captain Moreland does everything he can to talk his way out of this so as to avoid the pirates trying to find out that "Bertie" is really a girl in disguise. Then, Captain Moreland makes a ransom deal with Kuala; a large amount of money in exchange for their freedom as long as Captain Moreland is the one who writes the ransom note. Kuala agrees to let them go after they have ransomed them and have been paid as promised. When Kuala takes "Bertie" with them, Captain Moreland threatens not to write the ransom note unless they give him back "Bertie". To make sure he gets what he wants, Kuala places "Bertie" back with Captain Moreland and then returns to join the rest of his men as Captain Moreland helps "Bertie" up.
Then, Captain Moreland tells "Bertie" to keep quiet while the pirates decide which crew is going to take them. Then, a couple boys named Fritz and Ernst Robinson come to their rescue. As happy as he is to know that help is on the way, Captain Moreland insists the boys free "Bertie" first. Captain Moreland knows that he is out of harm's way since he is too valuable for the pirates to ransom. As the pirates start fighting and killing each other, Kuala and some of his men spot the boys helping the prisoners to escape, so, he orders his men to stop the fight and go after the boys. With "Bertie" free and Captain Moreland still tied up, the Captain insists they leave without him no matter as the pirates get closer. So, Captain Moreland stays behind as the pirates hold him while the others go after the boys and their prisoner.
Later, at night, the pirates set sail for England so as to ransom the Captain. Days later, Captain Moreland returns with a new ship and crew to return to the island and rescue his granddaughter and her saviors' family from the pirates by firing cannons at them and their ship; killing Kuala and his men as well. After vanquishing the pirates, Captain Moreland and some of his crew members come ashore on a lifeboat to reunite with his granddaughter as he allows Francis (the two Robinson boys' youngest brother) to see and keep his hat. After having a delicious meal served by Mother, he promises to take Ernst back to England to finish his studies in a university, where he has made donations for years, rather than a school as originally planned and promises the rest of the family to take them to New Guinea since it was their original destination from Bern, Switzerland before they were shipwrecked on the island by the pirates and a raging storm at the beginning but Mother feels that that the island has done so much wonders for her and her family that she decides to stay as their new home with the family and the animals; much to everyone's joy and surprise especially Father's, and the Captain notes that Father will likely be recommended as Governor of the new colony and that the family might have new neighbors too.
Captain Moreland is last seen waving good-bye to the Robinson family and his granddaughter, who has also decided to stay with the family as well to marry Fritz, as he takes Ernst on a lifeboat back to England for his education.
Captain Moreland's name is never mentioned in the movie and he is mostly referred to as "Grandfather" throughout.