The narrative opens in 1886 with John Baines, an earnest and unpolished young Englishman, delivering his farewell sermon in Tilehurst before departing for an East African mission. He is betrothed to Lucy Josling, a pretty and relatively well-read national school-teacher who is drawn to the adventure and romance of foreign parts. Despite the chilly disapproval of John's domineering mother, the engagement holds, and Lucy eventually embarks for Unguja to join him.
During her long sea voyage, Lucy finds an unexpected mentor and confidant in Captain Roger Brentham, a bronzed and worldly explorer. Their intense association on board leaves Lucy deeply unsettled, contrasting sharply with her mundane life and the rigid piety she encounters upon arrival. When she finally meets John, the stark realities of tropical Africa—rampant insects, stifling heat, and primitive conditions—threaten to overwhelm her romantic notions.
The couple pushes inland to Hangodi, a mission station situated high in the Ulunga hills. There, John throws himself into manual labour, preaching, and establishing a self-supporting community, while Lucy struggles against deep-seated homesickness and disillusionment with missionary life. Her growing disenchantment is exacerbated by the formidable presence of Ann Jamblin, a practical and sharp-tongued woman who arrives to aid the mission and easily eclipses Lucy's domestic utility.
As the region becomes engulfed in political turmoil involving rising Arab slave-traders and German colonial expansion, Captain Brentham reappears on an official mission to evacuate Europeans. Reunited with Roger amidst impending violence, Lucy faces a profound crisis of heart. The narrative develops through a rich tapestry of colonial politics, dramatic rescues, and stark personal trials, culminating in a delicate resolution where Lucy must choose between the secure, devoted duty of her missionary marriage and the lingering allure of an unfulfilled romance.
