When the redoubtable Sir Horace Stanton-Lacy is ordered to South America on business, he leaves his only daughter Sophy with his sister in Berkeley Square. Newly arrived from her tour of the Continent, Sophy discovers that her aunt's family is in desperate need of her talent for setting everything right: her uncle is of no use at all, the ruthlessly handsome cousin Charles has tyrannical tendencies that are being aggravated by his grim bluestocking fiancee; lovely cousin Cecelia is smitten with an utterly unsuitable suitor, a poet; cousin Herbert is in dire financial straits; and the younger children are in desperate need of some fun and freedom. Sophy has arrived just in time to save them all.