Axel Heyst, born of titled Swedish parents and raised in England, accepts his philosopher father's concept that life is essentially evil and that participation in it can only increase the evil and involve a man in trouble. The elder Heyst has taught his son that one's only condescension to life should be to watch it from a detached distance, never to partake in its action.
Such a philosophy ingrained in Heyst during his impressionable youth leads him to withdraw from life. His inheritance is small, but the income from it will support him in the Malay archipelago, where he has chosen to live the life of a wandering gentleman.
Fifteen years pass and nothing occurs to change Heyst's philosophy. He is now in his middle thirties and confirmed in his pattern of life. Then an unexpected happening throws latent forces in his character into conflict. He finds a man, Captain Morrison, in trouble with Portuguese authorities in Timor over a small fine. For lack of a trifling sum of money, Morrison is about to lose his ship.
Compassion for this fellow man in distress leads Heyst to offer his help. Morrison accepts but is so deeply grateful that he insists on Heyst joining his now-ransomed vessel. Heyst, embarrassed and ashamed of his involvement, goes along with Morrison. When Morrison decides to organize the Tropical Belt Coal Company, he makes Heyst his manager for the tropics, with headquarters on the island of Samburan, about three hundred miles from Sourabaya.
On a fundraising trip to England, Morrison catches a chill and dies. The Tropical Belt Coal Company folds, and Heyst, after dismissing company employees, continues to live on Samburan with no companion but a Chinese servant, Wang.
Heyst has no idea of the scandal being raised about him in Sourabaya, where Schomberg, the hotelkeeper, tells all who will listen that Heyst has cheated Morrison out of enormous sums of money and then sent him home to England to die. Schomberg says Morrison's death is murder and Heyst is the murderer.
Another master of a sea-going vessel, Captain Davidson, passes Heyst's isolated island at regular intervals, and being a humane person, he interests himself in Heyst; when passing Samburan, he swings in near enough to be hailed from the shore if Heyst should want anything.
Heyst, after eighteen months of solitary existence on Samburan following the collapse of the Tropical Belt Coal Company, hails Davidson and travels with him to Sourabaya on business. Knowing nothing of Schomberg's hatred of him or his malicious gossip, Heyst takes up quarters in Schomberg's hotel.
A troupe of traveling musicians, Zangiacomo's Ladies' Orchestra, is playing every evening for guests at the hotel. Heyst is annoyed by the wretched music, but out of boredom and mild curiosity, he ventures, one evening, into the room where the orchestra is performing. There he sees a young English girl, Lena, being abused by the dragon-faced wife of the orchestra leader. Immediately compassion rises in Heyst-the same emotion of pity and kindness that involved him with Morrison. He befriends the girl, and when he discovers that the obnoxious hotelkeeper, Schomberg, is pressing his attentions on Lena, he abducts her and carries her to his lonely island of Samburan.
Schomberg has hated and slandered Heyst for years; now he is filled with mad fury against the man. Although he and Zangiacomo are deadly enemies, he joins the orchestra leader in trying to hunt down the couple. Their search of the harbor is fruitless, and Schomberg returns to his hotel to plot revenge.
Schomberg has a colorless wife who appears to know nothing, be nothing, and care nothing for what transpires around her, but it is she who has helped the girl, Lena, to elope with Heyst. She is more perceptive than she looks.
Other visitors arrive in Sourabaya, a trio of desperadoes, who make their headquarters at Schomberg's hotel and quickly blackmail him into allowing illegal card games and other gambling in which they profit while amusing themselves. Mr. Jones, leader of the three, seems to be a gentleman of good birth yet so demonic in all his aspects that he appears more of a malevolent specter than a human being. His "secretary," Ricardo, a catlike villain with murder continually on his mind, complements Mr. Jones' talents. Their servant, a man called Pedro, strikes terror into Schomberg. The hotelkeeper sees himself being ruined and destroyed by these three. His own guilty conscience reacts on him and fills him with terrible fear. At last, in a confidential talk with Ricardo, he mentions Heyst and the pile of money Schomberg is sure Heyst has concealed in Samburan. Ricardo picks up this information and relays it to Mr. Jones, and with Schomberg's eager assistance the three set off for Samburan in an open boat.
Meanwhile, Heyst and Lena have enjoyed three months of idyllic happiness on Samburan. Yet both of them have reservations. Heyst realizes that he has again involved himself in life and regrets it. He feels that by opening his heart to Lena, he has opened the door to trouble and has been untrue to himself.
Although Lena has come to love Heyst with both gratitude and devotion, she sees that, in spite of himself, he regards her with mixed feelings. Her concern crystallizes into a desire to prove her love for him in some way which will forever allay his doubts and cause him to accept her fully. She has not long to wait; opportunity is on the way.
The three bandits arrive on Samburan more dead than alive. Their trip in the open boat has almost killed them, but under Heyst's surprised ministrations, they quickly recover and a deadly battle of wits ensues. Heyst soon realizes that these visitors are desperadoes of the worst sort. He knows that he and Lena are in terrible danger. Wang, the Chinese servant, compounds the difficulty of their situation by stealing Heyst's only weapon — a revolver.
Ricardo has concealed from his master, Mr. Jones, the fact of Lena's presence on Samburan. Mr. Jones has such an aversion to women that it borders on insanity. He abhors them. Ricardo does not share his feelings. He spies on Lena in her bedroom and makes a vicious sexual attack on her. Lena, with unexpected strength, repels his advances and wins his respect and admiration as well as his fierce affection.
Knowing that Heyst is in mortal danger, Lena has only one intention — she must disarm Ricardo and save Heyst. In order to accomplish her purpose, she deceives Ricardo into thinking that she is favorable to his plan for stealing Heyst's "treasure" and destroying both of the gentlemen. Lena knows that Heyst has no hidden cache of gold, but she plans to use Ricardo's infatuation and his avarice to disarm and destroy him.
On the last evening, Heyst sees that they are trapped. He is sure that he cannot escape but tries to save Lena by insisting that she put on a black dress and slip into the forest to hide. He hopes she will escape detection until morning, when she can go to Wang and the natives on the other side of the island for protection. Heyst leaves for a talk with Mr. Jones sure that whatever happens to him, Lena will be safe.
Lena has no intention of obeying Heyst. She knows that Ricardo carries a dagger strapped to his leg and that he intends to murder both Heyst and Mr. Jones this very night. She sits in the candle-lighted house waiting for Ricardo. When he comes, she charms him with her show of sweet compliance with all his wishes. He allows her to handle his dagger, which she conceals in the folds of her dress. She pushes out her foot for him to caress. He is in the act of kissing her white ankle when Heyst and Jones appear in the door. Heyst has just revealed to Jones that he has a girl here on Samburan. Jones is furious with Ricardo for concealing this information from him. He knows what a fool Ricardo is about women. Jones is in a murderous rage.
Mr. Jones shoots over Heyst's shoulder into the room. The bullet glances off Ricardo's head and pierces Lena's breast. Heyst is so taken back by what he thinks is Lena's betrayal of their love that he is confused and doesn't realize what has happened. Jones slinks away. Ricardo leaps up and rushes out into the night. The two are left alone. Lena is ecstatic. She has disarmed the enemy and saved Heyst; but Heyst turns from her remarking that it is all very "amusing." He is wounded by what he thinks is her falseness, yet his old habit of detachment prevents any angry denunciation.
Now she droops before him; there is a look in her eyes which seems to have awful portent. He catches her up and lays her on the bed, puzzling over what can possibly be wrong with her. At this moment, Captain Davidson, whose suspicions have been aroused by the discovery of Pedro's body in an open boat drifting off the island, comes in with the dagger, Ricardo's dagger, which he has picked up from the floor. Heyst, horrified at the idea of a secret dagger-thrust, tears Lena's clothes open and reveals the tiny black wound of the revolver bullet. Lena is dying and begs for some assurance from Heyst that she is at last permitted to enter the intimate inner circle of his love. He is unable to give the cry of love she wants to hear, and which he wants to give. His habit of isolation and detachment is still too strong. He does lift her up into his arms, and she mistakes this for the surrender she has given her life to win. She dies in an illusion of glorious triumph — a victory which transcends all suffering and all joy.
Meanwhile, Mr. Jones seeks out Ricardo and shoots him dead. Then he stumbles to the jetty where Wang has already shot Pedro and shoved off the boat. Either by accident or intention, Jones falls into the water and drowns.
Heyst makes his last sad pronouncement to Davidson: "Ah, Davidson, woe to the man whose heart has not learned while young to hope, to love and to put its trust in life!" Davidson tells the "Excellency," who has called him in to account for the Samburan tragedy, that Heyst then asked to be left alone with his dead. Later, Davidson discovers that the bungalow is on fire. Unable to do anything to save the property, he sees every building consumed. Later, with Wang, he sifts the ashes and knows that Heyst has died with his beloved Lena. "There was nothing I could do," Davidson tells the "Excellency."