Northern Spy is a thriller novel detailing the gripping story of two sisters caught on opposing sides of a conflict in Northern Ireland, 20 years after the Good Friday Agreement. Written by American author Flynn Berry, the book was originally published by Viking as part of Penguin Books on April 5, 2021. Northern Spy was chosen for Reese’s Book Club Pick and earned its place as an Instant New York Times Bestseller, as part of the New York Times Book Review Top 10 Thriller of 2021, and as part of the Washington Post Top 10 Thriller or Mystery of 2021. A graduate of Brown University and a recipient of the Yaddo fellowship, Berry is an author who specializes in thrillers and fiction and currently has three titles to her name, the most acclaimed of which is Under the Harrow. Throughout most of her works, Berry often explores themes of violence in history, family resilience and sisterhood, and the pitfalls of secrecy—themes that are also found within Northern Spy.

This study guide refers to the Northern Spy Penguin eBook edition distributed by Google Books and published on April 5, 2021.

Content Warning: The novel features extensive depictions of civil warfare, terrorism, and the aftermath of the Northern Ireland conflict (also known as the Troubles).

Plot Summary

Twenty years after the end of the Troubles, Northern Ireland is still locked in a deadly conflict between warring factions: the IRA, loyalist groups, and the British government. Tessa Daly, a news editor for the BBC and single mother living near Belfast, discovers that her sister, Marian, has been involved in an armed robbery led by the IRA. Floundering at the news, Tessa suspects the worst: The IRA has kidnapped her sister and are forcing her to commit crimes for them. No one can find or contact Marian, and Tessa fears for her life. When she meets with Detective Inspector Fenton, her fears, however, are not reciprocated. Worse, DI Fenton believes Marian is not a victim but rather an IRA member herself.

Tessa and her mother vehemently deny Marian’s involvement with the organization to friends and family, but others are not so quick to believe her innocence. As the police investigate Marian’s disappearance, incriminating evidence begins to pile up against her: She has been taking secret trips, one recently to Belgrade; a bomb had been discovered at St. George’s Market the last time she’d visited; she was keeping a burner phone hidden in her fireplace; she’s acted suspiciously while working as a paramedic; and the police have a recording of her confirming an arms drop with a notorious IRA figure, Cillian Burke. Try as Tessa might to stop it, doubt blooms. And when Marian finally reappears, she confirms the worst: She’s been an IRA member for the last seven years and taken part in many bombing missions—one of which involved using Tessa’s six-month-old son, Finn, as a cover.

Marian, however, proves full of surprises: Though she is an IRA member, she has become an informer for MI5, but her cover has been jeopardized by the recent armed robbery and police pursuit. She entreats her older sister to do the unthinkable: relay messages to Marian’s handler, Eamonn Byrne, and become an informer herself. Tessa staunchly refuses and tries to leave Northern Ireland behind to protect herself and her son, but with her ex-husband refusing to give his consent, Finn would have to stay behind with him should Tessa leave the country. Caught between two impossible choices, Tessa decides to cooperate with her sister. She reasons that the only way for Finn to truly be safe is for the conflict to stop, and the best way to do that, she surmises, is to stop it from the inside.

Thereafter, Tessa meets with Eamonn, a handsome agent who promises to keep her and her sister safe while she puts herself at risk on a regular basis. For weeks and months, Tessa innocuously meets with her sister and transmits the information to Eamonn. High on the success of thwarting IRA plans, Tessa lets her guard down and is unprepared to meet the men in Marian’s IRA unit at their cousin’s wedding. The leader among them, Seamus, takes an interest in Tessa, and before long, he insists on recruiting her to their cause. Once again, Tessa finds herself faced with an impossible decision: To refuse an invitation to join the IRA would cast suspicion and danger on Marian. To accept, however, would mean running the risk of her own death.

Love of family wins out, in the end, and as Tessa becomes further enmeshed in the IRA, the nuances of the conflict, of what is moral and just, become harder and harder to determine. Though she is meant to only play the role of a scout, Seamus pushes Tessa into a mission that would have a prominent British aristocrat murdered. Unable to refuse and unable to contact Eamonn for help, Tessa goes on the mission, feeling guilty and anxious, and plays her role dutifully—only for the assassination to fail. News of the attempt spreads wide, however, and before long, the IRA calls for a cease-fire.

While negotiations are under way, the people of Northern Ireland hold their breath and hope the peace will last. Tessa and Marian, meanwhile, enjoy their newfound freedom, believing their roles as informers to be over now that the peace talks are under way. But on a day like any other, two ski-masked men kidnap Tessa and Marian and bring them far away from their homes to a remote farmhouse where Seamus is waiting for them. With plastic sheeting already set for their corpses, Marian quickly realizes that they cannot talk their way out of this situation. She kills Seamus before he can, and the sisters run away, barely making it to the border. The farm where they were held explodes, and the world believes them dead. As Tessa and Marian recuperate from their ordeal, it is made clear that they can no longer return to Northern Ireland while the IRA still exists. Only death awaits them if they do. The police arrange for new identities, and the sisters decide to live in Ireland with Finn and their mother. Years later, when peace finally reigns in Northern Ireland, Tessa brings Finn back to visit their homeland without worrying about their safety. As she takes in the beautiful landscape, Tessa can breathe easy, knowing the conflict has finally reached its end.