Mollie is a young woman who recently inherited Monkswell Manor from her aunt. Along with her husband Giles, she has converted the estate into a guest house. She lacks practical experience in the hospitality industry, leading to considerable anxiety as their first guests arrive during a severe snowstorm. She is eager to make their new venture succeed and works diligently to keep the chaotic household functioning.

Giles co-owns the newly opened Monkswell Manor guest house with his wife Mollie. He assumes a protective posture over both the property and his spouse, taking on heavy physical chores like shoveling snow and fetching firewood. He has a slightly arrogant streak and quickly becomes jealous of the male attention his wife receives from the guests.

Detective Sergeant Trotter is an energetic policeman sent to Monkswell Manor to investigate a connection to a recent murder in London. Despite looking surprisingly young for his rank, he takes immediate control of the household. He is methodical in his interrogations, systematically questioning the trapped residents to uncover hidden connections to the crime.

Christopher is an energetic, youthful guest staying at Monkswell Manor. Claiming to be an architect, he displays a fascination with dark subjects and frequently sings tragic nursery rhymes. His erratic behavior makes him an unpredictable presence, though he eagerly offers to help Mollie with cooking and household chores.

Mrs. Boyle is a demanding, imposing woman who expects high standards of comfort. She is entirely displeased with the Ralstons' lack of experience, loudly criticizing the inadequate heating and lack of professional staff. Her abrasive personality quickly alienates her from the owners and the other travelers.

Major Metcalf is a middle-aged traveler with a steady, military bearing. He presents a sharp contrast to the complaining guests, maintaining a calm disposition during the severe snowstorm. He willingly pitches in with physical labor around the estate, investigating frozen pipes and shoveling snow while remaining observant of the household dynamics.

Miss Casewell is an independent traveler who presents a somewhat masculine appearance. She is highly guarded about her personal history and her reasons for returning to England from abroad. Rather than engaging in polite conversation, she prefers reading the newspaper and actively pushes people away when they ask probing questions.

Mr. Paravicini is an elderly, foreign traveler who becomes an unplanned addition to the Monkswell Manor group. Arriving without luggage or a reservation, he delights in his mysterious nature. He frequently makes unsettling jokes about the snow isolating the house from the rest of the world, heightening the anxiety of his hosts.