The Rose Code is a historical fiction mystery novel by Kate Quinn, published in 2021. Set in England during and just after World War II, the novel follows the experiences of three women who participate in Bletchley Park’s codebreaking operation, as well as their efforts after the war to uncover a traitor among their colleagues. Their stories highlight the social changes brought on by World War II, especially concerning gender dynamics. Kate Quinn is the author of several historical fiction novels for adults, including The Huntress and The Alice Network. Citations in this guide correspond with the first edition of The Rose Code published by HarperCollins.

Content Warning: The Rose Code and this guide include mention of sexual assault.

Plot Summary

The plot develops along two alternating timelines. The first starts in 1939 in England. As World War II begins, debutante Osla Kendall seeks to contribute to the war effort. After a short stint at a factory, she transfers to a top-secret codebreaking facility housed at Bletchley Park (BP). On her way there, she meets Mab Churt, an ambitious woman from a low-class background, also assigned to BP. Osla fills a secretarial position, though she later requests and receives a translation assignment, while Mab helps run codebreaking machines.

Mab and Osla board at the home of the local Finch family. Seeing that Mrs. Finch dominates her adult daughter, Beth, Mab and Osla help Beth become more social and help her get a position at BP. Beth, who has a strong mathematical mind, plays a key role in several codebreaking projects. She forms a strong friendship with Dilly Knox, her mentor at BP. Eventually, Beth breaks with her family, and she, Mab, and Osla move out.

Mab, Osla, and Beth each pursue romantic relationships. Osla dates Prince Philip of Greece. When she is forced to cut off communication for security reasons, he leaves her for Princess Elizabeth. Mab falls in love with and marries Francis Gray, a war poet, whom she learns to trust despite lingering trauma from an earlier, abusive relationship that resulted in a daughter, Lucy. Beth develops feelings for Harry Zarb, a codebreaker at BP. They begin an affair once Harry’s wife, Sheila, explains that she and Harry share an open marriage. Under mounting pressure to fight from civilians who know nothing of his secret codebreaking, Harry enlists despite Beth’s objections.

In November 1942, Mab, Francis, Lucy, and Osla take a holiday in Coventry, where Lucy and Francis are killed in an air raid. Mab blames Osla for letting go of Lucy during the raid. Later, Mab learns that Beth decrypted a message identifying Coventry as target and failed to warn them. Devastated, Mab withdraws from her friendships and drinks heavily.

Following Dilly’s death from cancer in 1943, Beth works on an unsolved code, which she nicknames the Rose Code. In May 1944, her findings reveal the presence of a traitor at BP; she tries to contact the commander, but he refuses to see her. Giles Talbot, a friendly man who is the traitor hinted at in the Rose Code, frames Beth and has her committed to Clockwell Sanitarium. Mab leaves for a post in London and Osla stays at BP until the war ends.

The second timeline begins in 1947. Beth smuggles messages out of Clockwell Sanitarium to Osla and Mab, asking for help and telling them that someone at BP framed her. Still estranged, Mab and Osla meet to discuss the messages and decide to visit Beth. The day before their visit, Giles visits Beth and threatens to have her lobotomized unless she tells him where she hid the Rose Code. She refuses. The next day she explains everything to Mab and Osla, who help her escape.

Needing more evidence to convict Giles, who is now Osla’s fiancé, they call together several BP alumni to help them crack the rest of the Rose Code. Mab is surprised when her second husband shows up to help; neither realized the other did similar work during the war, and their realization opens the way to newfound intimacy.

They crack the code a few hours before the royal wedding between Philip and Elizabeth. Hearing that Beth escaped, Giles goes on the run, but the group catches him at a train station. A nearby officer arrests them all, but Osla sorts out the confusion with a call to Philip, who remains her friend. Giles is convicted. Mab goes on to raise a family, Osla marries and lives out her dream of writing satire, and Beth continues to break codes for the government while seeing Harry frequently. They visit BP one last time.