A producer at the BBC and mother to a new baby, Tessa is at work in Belfast one day when the news of another raid comes on the air. The IRA may have gone underground in the two decades since the Good Friday Agreement, but they never really went away. As the news reporter requests the public's help in locating those responsible for the robbery, security footage reveals Tessa's sister, Marian, pulling a black ski mask over her face. The police believe Marian has joined the IRA, but Tessa is convinced she must have been abducted or coerced. When the truth about Marian comes to light, Tessa is faced with impossible choices that will test the limits of her ideals, the bonds of her family, her notions of right and wrong, and her identity as a sister and a mother. Walking an increasingly perilous road, she wants nothing more than to protect the one person she loves more fiercely than her sister: her infant son, Finn. Riveting, atmospheric, and exquisitely written, Northern Spy is at once a heart-pounding story of the contemporary IRA and a moving portrait of sister- and motherhood, and of life in a deeply divided society.