A crusading priest struggles to build a mission in China.

In 1938, Monsignor Sleeth is about to conclude a week-long visit to the Tweedside, Scotland parish of elderly priest Francis Chisholm, whom he considers unfit. Chisholm asks Sleeth to reconsider his recommendation that he be forced to retire, and reminds Sleeth that he was boyhood friends with Bishop Angus Mealy, who ordered the investigation. Sleeth asserts that Chisholm's sermons are too eccentric, but Chisholm, who has been home for only a year after decades of service as a missionary in China, wishes to remain in Tweedside with his ward Andrew. When Sleeth retires for the night, he finds Chisholm's diary and begins to read: In 1878, Chisholm is a young boy who is loved by his fisherman father Alex and mother Lisbeth. The Catholic Alex has difficulties in the Protestant village, however, and one night, he is attacked. As Lisbeth helps her wounded husband home, they are drowned in a raging river, and Chisholm goes to live with Alex's cousins, Polly and Ned Bannon. Polly and Ned provide the boy with a stable home, and as he grows up, Chisholm falls in love with their daughter Nora. Despite Chisholm's profession of love, Nora fears that he will become a priest, as Polly wants, and when he returns to college with Angus and bids farewell to his best friend, atheist medical student Willie Tulloch, Nora despairs. Chisholm continues his studies but is mystified by a letter from Polly asking him not to come home during the summer. Finally Chisholm learns that Nora, heartsick at her imagined abandonment, has given birth to an illegitimate daughter. Chisholm rushes home but Nora dies before his arrival. Accepting his vocation, Chisholm becomes a priest, but fails at his first two positions. His advisor, Reverend Hamish MacNabb, encourages Chisholm to become a missionary, and soon the young priest sets off for the village of Pai-tan in the Chekkow province of China. Upon his arrival, Chisholm is greeted by the hypocritical Hosannah and Philomena Wang, who storm off upon Chisholm's warning that he is not interested in the "rice Christians" who attend church only to receive an allotment of rice. Alone, Chisholm struggles to build his mission, until one day he is joined by Joseph, a young Chinese Catholic. Joseph aids Chisholm in his labors and they soon receive a box of medical supplies from Willie. Later, Mr. Pao appeals to Chisholm for help with Chia-Yu, the child of the local mandarin, Mr. Chia. Chisholm goes to Chia's lavish home and tends to Chia-Yu, whose infected arm requires surgery. Chisholm's medical treatment cures the lad, but he gently refuses Chia's offer to convert to Christianity, saying that he cannot accept a soul in exchange for services rendered. Instead, Chia gives him a land grant and the materials and labor with which to build a fine mission. After two years the mission is completed, and nuns Mother Maria Veronica, Sister Martha and Sister Clotilde arrive to start a school. Maria Veronica, the daughter of an aristocratic Austrian family, looks down upon the humble, unworldly Chisholm and rebuffs his attempts at friendship. Chisholm is impressed by her competence, however, and the mission flourishes. When the Wangs return, they trick Maria Veronica into trusting them, despite Chisholm's warnings, and rob the sisters. Maria Veronica is still reluctant to trust Chisholm, and her suspicion of him deepens upon the arrival of the atheistic Willie. During Willie's visit, a war between imperial and revolutionary forces begins, but Chisholm refuses to abandon the mission. He and Willie aid the wounded revolutionary soldiers in the village, but when they learn that the church has been shelled, they rush back. On the way, Willie is mortally wounded, and Maria Veronica is shocked by Chisholm's refusal to force Willie to accept God as he dies. At great risk to himself, Chisholm blows up the cannon of the imperial forces, and the war ends. Soon after, Angus, now a monsignor, visits and expresses displeasure at the burned-out church and Chisholm's plain lifestyle. The contrast between the pompous Angus and the humble Chisholm finally makes Maria Veronica understand how truly good he is, and after Angus departs, she begs Chisholm's forgiveness for her harshness. Chisholm easily forgives her, and with help from Maria Veronica's wealthy family, their church is rebuilt. Ten years pass as the two become friends and work hard to guide their flourishing parish. One day, Chisholm learns of the arrival of Methodist missionaries Dr. Wilbur and Agnes Fiske, who are surprised by the sincere welcome they receive from their Catholic "rival." The time eventually comes for Chisholm's return to Scotland, and although he anticipates meeting Nora's grandson Andrew, his heart aches at the thought of leaving his beloved China. Maria Veronica and Joseph can barely bid farewell to their great friend, and at the dock, Chisholm blesses the many people who have come to wish him well. Back in Scotland, Sleeth finishes reading Chisholm's diary by the light of dawn, and as he prepares to leave, he confesses impinging on Chisholm's privacy. Chisholm is flattered by Sleeth's attention to his "ineffectual" life, but Sleeth sincerely tells the older man that he feels honored to have met him and assures him that he will be allowed to remain at Tweedside.