Cassie, the youngest of six daughters in the Wilton family, is bold, bright, and ready to enter society. There's only one problem: her older sister Lenora, whose extreme shyness prevents her from attending many social events. Lenora is now entering her third season, and Cassie has no choice except to wait her turn.

Evan Glenside, a soft-spoken, East London clerk, has just been named his great-uncle's heir and, though he is eager to learn all that will be required of him, he struggles to feel accepted.

A chance meeting between Evan and Lenora promises to change everything, but when Lenora proves too shy to pursue the relationship, Cassie begins to write Mr. Glenside letters in the name of her sister but her good intentions may lead to disaster.

As secrets are revealed, the hearts of Cassie, Evan, and Lenora are tested. Will the final letter sent by the vicar's daughter be able to reunite the sisters as well as unite Evan with his true love?