A Damsel In Distress starts out at Belpher Castle, home of the Earl of Marshmoreton and his family. The Earl is a widower whose son and heir, Percy, is about to reach his majority on his 21st birthday. He also has a daughter, Maud, who is twenty. Also in residence at the castle is the Earl's widowed sister, Lady Caroline Byng and her stepson, Reggie. The Earl is a simple soul whose pride and joy is his rose garden, where he would happily spend most of his days cultivating blooms and killing slugs. Unfortunately, his peace is being constantly disrupted by Lady Byng, who insists that he spend time writing a history of the Marshmoreton family, aided by the efficient secretary, Miss Faraday, whom she has provided for him. Lady Byng has an extremely forceful personality, and the Earl is generally cowed by her, so ends up unhappily working on the book he loathes. Meanwhile, Lady Maud has for the past year been a virtual prisoner at Belpher, kept under careful surveillance by her aunt. This is due to the fact that a year ago Maud was visiting friends in Wales and met an American man whom she fell in love with. When she gets wind if this, Lady Byng is aghast for two reasons: the young man is unsuitable, being a mere secretary to his wealthy uncle, and also, Caroline Byng has been nursing hopes of a match between Maud and Reggie. She whisks Maud back to Belpher, determined to keep her away from this objectionable man until her niece gets over her infatuation. Percy, pudgy and stodgy, has all the snobbery and class consciousness that his father lacks, and agrees wholeheartedly with his aunt's actions. There is, however, another problem with Lady Byng's plans: Reggie, though very fond of Maud, is in love with Alice Faraday, his uncle's secretary.
The action starts when Maud receives a secret letter from Geoffrey, the man she loves. He has returned to England (his uncle having been travelling) and asks her to meet him in London. Thrilled by the prospect of seeing him after a year apart, she tries to think up a way to sneak to the city without her aunt finding out. She knows that Reggie is driving into London the following day to pick up Percy and bring him home for the birthday festivities, so she asks him to take her with him; she'll meet with Geoffrey and then take the train back to Belpher before anyone realizes she was gone. Reggie agrees, and the next day they make their way to London.