Mary MacEachran enters service at a sprawling English estate where Constance Trentham oversees her adjustment among rigid household hierarchies. Sir William McCordle and Lady Sylvia McCordle host a weekend gathering of wealthy guests whose polite performances mask friction and resentment. Henry Denton, a curious valet, disrupts below stairs order with intrusive questions while Elsie guides Mary through hidden rules of service. After a missing object unsettles staff tensions, a murder shocks the household, drawing Inspector Thompson into a chaotic investigation that exposes fractures between upstairs and downstairs, as suspicion spreads through servants and guests alike.