May is a 25-year-old woman of privilege who has been institutionalized by her family for having two children out of wedlock with a man deemed beneath her station. She joins the covert program to escape the abusive conditions of the mental healthcare facility where she has been confined. An articulate and observant woman, she begins a journal to record her experiences and assert her intellectual autonomy in her new reality.

An intelligent, honorable officer in the US Army, Captain Bourke acts as an amateur ethnographer with a genuine curiosity about Indigenous cultures. He remains duty-bound to the army's expansionist policies and privately views the bridal program as a preposterous experiment. He is protective of May, recognizing her refinement and education.

The pragmatic and stoic "Sweet Medicine Chief" of the Northern Cheyenne, Little Wolf initiates the bridal program out of a desperate desire to ensure his people's survival. He is a dignified leader who manages the encroachment of white expansionism with tactical logic grounded in Cheyenne tradition. As a husband, he exhibits patience and eventual affection toward his new bride.

Seminole is a multiracial man of Cheyenne and white descent who uses his fluency in multiple languages and his cultural knowledge to manipulate others for personal gain. Depraved and predatory, he introduces whiskey to the peaceful camp, triggering widespread violence. His familial ties to the chief shield him from traditional tribal justice.

Phemie is a statuesque, formerly enslaved Black woman who escaped the South via the Underground Railroad. Fiercely independent and proud, she views the government's reservation policies as another form of bondage. Upon arriving in the Cheyenne camp, she rejects traditional women's labor and pursues the life of a hunter and warrior.

Helen is an eccentric English ornithologist and artist who joins the program primarily to fund her research for a book on American birds. Frequently dressed in a man's knickerbocker suit, she observes her surroundings with scientific detachment. Her artistic talent quickly earns her a respected position within the tribe as a creator of powerful protective symbols.

Martha is a kind-hearted hospital assistant who faces dismissal and chooses to enlist in the program alongside May. Initially clumsy and ill-prepared for frontier life, she represents the conventional 19th-century woman struggling to adapt. Over time, she undergoes a personal transformation and discovers unexpected resilience.

Margaret and Susan Kelly are red-headed, freckle-faced identical twins from Chicago's Irish underclass. Facing a lengthy prison sentence for prostitution and grand theft, they join the program to escape incarceration. Witty and pragmatic, they treat the dangerous endeavor as an adventure and quickly establish a gambling enterprise within the camp.

A woman of ruined gentry from the South, Daisy is initially defined by her overt racism and cynical demeanor. She holds tightly to the prejudices of the Old South and treats the non-white members of the group with open contempt. A brutal trauma in the camp shatters her bitter exterior, leading to a profound shift in her character.

Narcissa is a stern, evangelical Episcopalian who joins the program with no intention of fulfilling the matrimonial bargain. Instead, she views the expedition purely as an opportunity to convert the Cheyenne. Sanctimonious and highly judgmental, she actively resists integration and frequently clashes with the more adaptable women in the group.

Sara is a young, pretty, and deeply timid nonverbal girl who has been broken by an unknown trauma in white society. Upon integrating into the Cheyenne camp, she begins to blossom, finding her voice by learning to speak the Cheyenne language and embracing her new environment.

A corpulent and indolent Episcopalian missionary, Reverend Hare represents the failures of institutional religion on the frontier. His rigid approach to the mass wedding ceremony clashes directly with Cheyenne traditions. He proves cowardly during camp crises and is ultimately disgraced for his hypocritical behavior.

A rough-spoken, pragmatic individual who disguises herself as a male muleskinner for safety and economic independence. Having previously lived among the Cheyenne, she is fluent in their language and customs. She serves as a critical link between the white and Indigenous worlds, undertaking dangerous courier missions.

Quiet One is the senior wife of Chief Little Wolf. Deeply hostile to the arrival of the white brides, she resents May's presence in their shared living space. Her animosity highlights the internal tensions caused by the forced integration of the women into the established Cheyenne social structure.

Feather on Head is the friendly second wife of Chief Little Wolf. Unlike her hostile counterpart, she helps ease May's transition into the daily labor and routines of Cheyenne domestic life, offering a gentler introduction to the tribe's complex marital structures.

Gretchen is a robust and capable Swiss immigrant who brings physical strength and practical skills to the group of brides. She firmly establishes her presence in the camp by publicly defeating Jules Seminole in an arm-wrestling match, and she frequently allies with the other women to build communal spaces.

Brother Anthony is a humble Benedictine monk who arrives at the winter camp to provide spiritual guidance. Unlike other missionaries the group has encountered, his genuine devotion and self-denial earn the respect of the Cheyenne. He provides comfort to the traumatized white women and serves as a quiet witness to the unfolding tragedy on the plains.

J. Will Dodd is a modern-day journalist and the great-grandson of May Dodd. Prompted by the discovery of an old letter, he embarks on a quest to uncover the truth about the ancestor his family dismissed as mentally ill. His research leads him to the Tongue River Indian reservation, bridging the gap between his family's suppressed history and the preserved truth.

Harold is a 96-year-old Northern Cheyenne tribal historian. For over a century, his people have carefully safeguarded May Dodd's journals within their sacred Sweet Medicine bundle. He facilitates the sharing of this history with May's modern descendants, ensuring the true story is known.