The novel opens with Mr. Tench, an English dentist living and working in a small Mexican town, heading from his home to the riverside to pick up a canister of ether that he has ordered. The ships have come in, and Tench stands in the blazing Mexican sun, watching the rickety boats and continually forgetting why he has come to the river. He meets the stranger, a mysterious man who is waiting for a boat to Vera Cruz. Tench is interested in speaking with the man because he speaks English and, upon learning that the stranger has a bottle of contraband alcohol with him, becomes even more interested. Tench invites the stranger back to his house to share a drink.
At Tench's home, the two men talk and drink for some time. Tench tells his guest that he left behind a family in England, but he has given up writing letters to his wife. The stranger looks like he has not been taking good care of himself. He seems wary and somewhat anxious. He makes strange comments that make Tench pause and wonder about the man.
The men are interrupted by the boy who knocks, seeking help for a woman, his dying mother. Reluctantly, as if he had no choice, the stranger agrees to accompany the boy back to his house. He is aware that doing so will mean that he will most likely miss the boat to Vera Cruz. As he takes his leave of his host, the stranger tells him that he will pray for him. After his guest departs, Tench discovers that the stranger has left his book behind. He opens it and finds that it is a religious book about a Christian martyr, an illegal document in this state. Unsure of what it is, but dimly aware that he shouldn't have it in his possession, Tench hides the book in a little oven. He suddenly remembers that he forgot to pick up the canister of ether, and runs down to the river only to find that the ship has left the dock and is drifting downriver. On the boat, a young girl sings a sweet, melancholy song. She feels free and happy but she does not know why. Elsewhere, the stranger, walking along with the boy, hears the boat's whistle and realizes that he has, in fact, missed it. He feels despondent at being unable to leave, and angry towards the boy and his mother for keeping him from his boat.
The stranger is a priest, the unnamed protagonist of the novel, and Greene introduces him to us in a strange way: although he employs a third-person narrator to tell his story, he refrains from having this narrator directly tell us who this character is at first. Like Tench, we are left to observe this mysterious figure and make inferences about him based on his strange manners, his awkward behavior, his secretive ways. As a result, we initially meet this character feeling puzzled by him, perhaps even suspicious of him, and for good reason. The novel, in many ways, is very much about the question of how people come to terms with this character, how people evaluate his choices and his attitudes. For example, what do we make of the fact that he agrees to act honorably and help the boy but only does so grudgingly once he learns that it has inconvenienced him?
Meanwhile, Mr. Tench is a portrait of mental and spiritual numbness. It is fitting, therefore, that his errand is to pick up a canister of anesthetic. Indifferent, detached, absent-minded, almost vacant, Tench is a kind of spiritual thermometer for the novel, an indicator of the general atmosphere of quietude and apathy. Tench also serves here as something of a contrast to the priest, arguing that it is useless for him to journey with the boy to visit his dying mother. She is going to die anyway, he reasons, so what would be the point? Mired in a feeling of utter futility, Tench attaches little importance to action of any kind, indicated by his inability to complete a simple errand, as well as his curious refusal to leave Mexico, a place he dislikes. Although he accompanies the boy reluctantly, the priest still feels a sense of duty and retains a feeling that his actions are of some importance and consequence.
We should not, however, make too much of the contrast between the two men: it is also important to note that, after he picks up the religious book, Tench grows "thoughtful" for a moment. Tench may be frozen, but he is not dead, and the hope that even the most callous and indifferent people are still capable of spiritual regeneration is an important idea in this novel. It is a theme that will receive much fuller treatment as the story progresses. Although Tench is not incredibly important to the plot itself, Greene occasionally returns to him briefly over the course of the novel.