American heiress Jennie Leslie, the Honorable Cecil Winthrope, and the alcoholic Thomas Blake are washed ashore on a deserted island after a shipwreck. At first, Jennie sticks close to Cecil, preferring his upper-class British breeding to Thomas' man-of-the-people approach. Cecil, however, turns out to be completely ineffective when it comes to survival, and so both he and Jennie depend on Thomas for food, clothing, and protection. The surroundings bring out the "caveman" in Cecil in one respect, however; he tries to rape Jennie. During the attempt, which takes place during a storm, Cecil is crushed by a falling tree, and just before he dies, he reveals that he was merely a valet posing as an aristocrat. Then, Jennie and Thomas realize that they are in love with each other, and when a rescue ship picks them up, they begin making plans for their marriage.

Thomas Blake, American engineer, was half drunk. He stood at the ship's railing, and he eyed the beautiful young lady, who stood adjacent with bibulous approval. He stooped, unsteadily, to recover a book the young lady had dropped. He chuckled as the lady promptly turned her back to him, and greeted Cecil Winthrope. The friendship between Jenny Leslie and Cecil Winthrope began early aboard ship. Cecil cultivated that friendship for he needed money, and he believed that this American heiress would supply it. An open boat without oars tossed on heavy seas; reclining in the bottom is Thomas Blake insensible from drink. Perched each in the bow and stein, are Miss Jenny Leslie and the Honorable Cecil Winthrope. Fate has cast the three adrift on a waste of waters, sole survivors of a wrecked ship. The little craft finally lands on the desert coast of eastern Africa. Thomas Blake came to his senses and he suffered a severe headache. This and the fact that his supply of whiskey was low, made him really ill-tempered. However, Thomas resolved to share his remaining stimulant with the man and woman. When they refused to partake thereof, Thomas was just as well satisfied, and drained the contents of his flask. Feeling better, Thomas Blake sized up the situation. He had always sized up previous situations and had mastered them by sheer brute force. Blake growled at the Honorable Cecil and Jenny Leslie, who seemed to be helpless to follow him into the jungle and to explore the island. They obeyed. As hunger came to Thomas Blake, he fashioned himself a club and went forth in search of food. The Honorable Cecil and Miss Jenny Leslie reclined at the foot of the tree and both fell asleep. Along the branch of the tree a python was reclining. Slowly it glided down the tree and toward the sleeping woman. Soon the darting fangs were very close to the unconscious girl. Then Thomas Blake returned, and clutching the reptile in his bare hands he strangled it. That night Thomas Blake selected a tree and ordered Miss Leslie into it. Despite the protestations of Winthrope and Miss Leslie they were forced to the refuge. In the dead of night, a lion prowled at the foot of the tree and endeavored to reach the cowering persons in its branches. It remained for Thomas Blake to get food, carry water, and to order the march for the next day. The experiences of the three with lions, tigers, herd of wild elephants, rivers swarming with crocodiles, are too many to narrate. When the Honorable Cecil sacrificed all the priceless matches in order to light a cigarette, Blake punished him. He also confiscated Winthrope's monocle, which he used to light fires. Blake, with little to no assistance from Winthrope, fashioned a rude dwelling, in which they lived comfortably, and he built a special apartment for the woman. Jealous of Blake and despite the fact that Blake had saved their lives many times. Winthrope whispered to Jenny of the constant danger he believed she was in from the association of this so-called "brute." Jenny believed Winthrope and feared Blake. Winthrope endeavored to force his way into her room in the dead of night, but was frightened away by wild animals. In the morning he told her that it was Blake. Time passed, and Jenny Leslie came to know the cowardly nature of Winthrope. Once she informed Blake: "I believe I have more cause to fear the gentleman than I have to fear the brute." Thomas Blake only grinned, and he ordered Jenny to discard her skirt for a dress fashioned from skins. "I want the skirt for a signal of distress, for some ship may pass here sometime," he said. He took the skirt and affixed it to a long pole placed on the highest peak along the coast. One night Blake announced that he would go in search of game, and that same night Winthrope plotted against Jenny Leslie. Despite the mutterings of the approaching storm, he tried to break through the rude door leading to Jenny Leslie's room. The tropical storm broke quickly and wind and rain lashed the dwelling. Trees were blown down, and one, as if directed by an avenging hand, pinned Winthrope, crushed and bleeding, underneath, as it crashed to earth. He was found the next morning by Blake, who cut away the timber, and who tried with Jenny Leslie to revive Winthrope. "I have a confession to make," whispered Winthrope, "Me real name is Hawkins. I was valet to a title Englishman. I sold his wife's jewels, and I went forth determined to pose as a gentleman and to marry money." Then Winthrope died. Jenny Leslie was left alone with Thomas Blake. As the weeks went by, the woman learned more of the heart of gold hidden underneath a rough exterior. And then one day the whistle of a steamer sounded along the African coast. The skirt tied to the pole had been seen by the ship's captain and the rescue was near. Thomas Blake, American engineer, and Miss Jenny Leslie, American heiress, who was once selfish and supercilious, stood together awaiting the landing of the rescue party. Thomas Blake was bashful; he had always been so with women. The girl looked into the caveman's eyes. "I love you," she whispered. "I love you, too," exclaimed Thomas Blake, as he gathered the lovely form of the girl into his mighty arms and held her closely.—Moving Picture World synopsis