Shirley Davenport is as much a patriot as her four brothers. She, too, wants to aid her country in the war efforts, but opportunities for women are limited. When her best friend Joan informs her that the Coast Guard has opened a new branch for single women, they both enlist in the SPARs, ready to help protect the home front. Training is rigorous, and Shirley is disappointed that she and Joan are sent to separate training camps. At the end of basic training, Captain Webber commends her efforts and commissions her home to Maine under the ruse of a dishonorable discharge to help uncover a plot against the First Lady. Shirley soon discovers nothing is as it seems. Who can she trust? Why do the people she loves want to harm the First Lady? With the help of Captain Webber, it's a race against time to save Mrs. Roosevelt and remain alive.