1855. When Doctor Thorne's penniless niece, Mary, is excluded from the wedding preparations of her childhood playmate, she probes her uncle for the truth of her birth. She is devastated to learn that she is the illegitimate child of his late brother. It seems she has neither breeding nor fortune. This is a problem, as Mary and the heir to the Greshamsbury Estate, Frank, have fallen in love. Frank is under strict instructions from his over-bearing mother, Lady Arabella, to save his family from financial ruin by marrying money. Frank's mother schemes to separate the two lovebirds, encouraging her son to woo the wealthy American heiress, Miss Dunstable. Meanwhile, Doctor Thorne acts as both physician and business advisor to railway millionaire, Sir Roger Scatcherd, in whose hands the fate of Greshamsbury lies and who is rapidly drinking himself into an early grave. Frank finally plucks up the courage to propose to Mary and Doctor Thorne gives him his blessing, but not before he has filled him in on the scandalous truth surrounding her birth. Lady Arabella continues her persecution of Mary, and is furious when Frank tells her he is set on marrying Doctor Thorne's penniless niece.