Each March girl is on a "pilgrimage," a journey of moral transformation that will mark her coming of age. The point of embarkation is Father's letter.

Each girl responds to it with a vow to "be better" and do her duty to the household. The novel depicts progress made as the girls undergo, separately or together, a series of trials by which selfish temptations are overcome. A persistent theme is that selfless, spiritual values bring happiness and comfort. When the several sisters first voice discontent, Beth recalls how Meg had said that "we were a deal happier than the King children, for they were fighting and fretting all the time, in spite of their money."

In the narrative the Golden Rule is invoked, but the goal is family approval rather than religious salvation.

Amy, who at first kept back a little money for herself at Christmas...