Setting is the Battle of the Alamo February 23 to March 6, 1836, in San Antonio, Texas, and afterward, when Santa Anna occupies the mission. Hannah has just returned from Scotland, where she was assisting the famous Scottish surgeon James Braid, the father of the use of mesmerism during surgery. She meets the narrator, journalist Edward Calmes, who works for Blackwell's Magazine in Edinburgh Socotland.

Hannah visits President Andrew Jackson at his invitation, and become a maid and undercover double-spy for the State of Texas. In her plan she escapes the Alamo when it's attacked by Santa Anna's troops. She uses her linguistic ability to speak Spanish, and she pretends to be from Spain, as she is light skinned, but she infiltrates the Alamo Mission, while Sana Anna occupies it, to collect critical information needed by the Texans to defeat the invaders from the south.