The Alice Network

Yes, in part. The novel is inspired by a real World War I spy ring known as the Alice Network, which operated in German-occupied northern France gathering military intelligence for the British. Its real-life leader, Louise de Bettignies (code name "Lili"), and British intelligence officer Cecil Aylmer Cameron both appear in the book as historical figures. The two protagonists, Eve Gardiner and Charlie St. Clair, are fictional.

No. The Alice Network is a standalone novel. Kate Quinn's other WWI- and WWII-set historical novels, such as The Huntress and The Rose Code, are separate standalone books rather than sequels or entries in a shared series.

The novel alternates between two timelines: 1915, when Eve Gardiner is recruited into the Alice Network spy ring in German-occupied France, and 1947, when Charlie St. Clair searches for her missing cousin in the aftermath of World War II.