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 since their father has decreed that only one Wilton girl can be out at a time, 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 in a new town and in his new position.

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. Her good intentions lead to disaster when Cassie realizes she is falling in love with Evan. But then Evan begins to court Lenora, thinking she is the author of the letters.

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?