Oil is discovered on the Countess de Elberca's estate in a mythical Spanish American country. Mercedes McDonald, her niece, falls in love with Sandy Buchanan, a young Scotch engineer hired by the countess. Don Felipe, a neighbor in need of money to avoid arrest for embezzlement, conspires with his nephew, the Duke of Othomo, for the latter to wed Mercedes. The aunt approves the suit. Felipe and Othomo attempt to kill Mercedes' sweetheart, but Buchanan, with the aid of her brother and a traveling American circus, foils their plans. Felipe and Othomo are killed by the circus animals, and the aunt consents to Mercedes' marriage to Buchanan.

During World War I, young Dorothy Grant comes home from finishing school and informs her parents that she is going to contribute to the war effort by organizing a "Girls Aviation Corps". She has uniforms made and hires a veteran of the Spanish-American War to teach her "cadets" military routines and drills. Her father owns a munitions factory and is always telling her to be on the lookout for spies. She convinces herself that the family butler, Williams, is a spy because he cuts his grapefruit in an odd way. It turns out that Williams isn't a spy but the people whom Dorothy least suspects are in fact spies, and they discover that Dorothy knows the password to get into the factory after hours.

Wealthy Jarvis Pendleton acts as benefactor for orphan Judy Abbott, anonymously sponsoring her in her boarding school. But as she grows up, he finds himself falling in love with her, and she with him, though she does not know that the man she has fallen for is her benefactor.

Paul Drummond is adopted into a Franciscan Mission in California. Becoming of age, he believes he has a call to the priesthood. While at Theological Seminary, he becomes doubtful of his future and on the advice of his old Confessor he decides to become a physician. His roommate at college cherishes a little Crucifix given him by his mother. This Crucifix figures in the drama of events that finally convince Paul that the priesthood is his true calling.

While traveling out West, John Maddox rescues Beatrice Clive, an English girl, from a dangerous cliff. Six years pass, during which Maddox becomes a wealthy rancher. Upon returning, Maddox finds the Bulverton estate is in jeopardy and Beatrice is engaged to the villainous Sir George Trenery due to financial desperation.

Lucy Hegan, the proprietor of a settlement house for the poor, is engaged to Hugh Gordon, the head of a large pharmaceutical and chemical firm who, unknown to Lucy, is also the ringleader of a powerful drug and white slave operation in the Chinese quarter.