In the opening scene, set in 1973, the Troubles result in the death of her younger brother when they are children. The film jumps forward to 1993 Belfast, Colette is living with her mother and brothers. After a failed attack in London, Colette is arrested and offered a choice: either she spends 25 years in jail, thus losing everything she loves including her young son, or she becomes an informant for MI5, spying on her own family. Colette agrees to do so. An MI5 officer, Mac, is assigned as her handler. In return Mac offers a new identity to her after a period working for MI5. Soon Mac learns that his superior Kate Fletcher is using Colette to protect her mole inside the Irish organization. Mac tries to find the identity of the informer and protect Colette. A romantic interest develops between Mac and Colette, as they kiss passionately at their weekly meeting. Meanwhile, Kevin is an IRA enforcer, who realizes there is a mole within Greg's family. He gets closer and closer to Colette, while Mac's superiors refuse to remove her from danger. Finally, Kevin realizes that either Connor or Colette is the mole. Greg gives passive consent for Kevin to take action. Connor is tortured, but gives no information. Just as Connor is about to be executed, Kevin calls it off, determining Connor is not the mole. At the same time, Mac breaks in to secret archives and determines that the original mole is Colette's mother. He understands that he has been used by his superiors, who were only interested in Colette because she would have hidden her mother's treachery. Mac makes a phone call to Ma, informing her that the IRA is coming for Colette, and that Colette was recruited in order to protect Ma. However, as Kevin arrives, seemingly there to get Colette, Ma goes outside and enters Kevin's car. She is later shown to have been executed. Kevin had determined Ma was the mole, hiding Colette's involvement. Mac makes a phone call to Colette, warning her that he can get her and her son out. He is acting alone, outside the permission of his superiors. Given there romantic feelings for each other, it appears that they will make a run for it together. Mac arrives in his car. Colette, now no longer an IRA suspect, is relaxed and playing with a dog. Mac's cell phone rings in his car. When he answers it, a car bomb explodes, killing him. The film ends with Colette getting into a car with her brother Connor, and her son. Connor tells Colette that "it's done" and they have to leave. It becomes evident that Colette was playing Mac, and set up his death. Her true IRA colors are revealed, and her brother helps her and her son make their escape from British authorities.
, the film holds an 83% approval rating on Rotten Tomatoes, based on 90 reviews with an average rating of 6.95. The website's critics consensus reads: "A tense, thought-provoking thriller, Shadow Dancer is bolstered by sensitive direction from James Marsh and a terrific performance from Andrea Riseborough." British film magazine Empire giving it a score of 4 out of 5 stars, calling it "an intelligent and emotionally charged spy drama". The Guardian called it "a slow-burning but brilliant thriller about an IRA sympathiser forced to become an informant by MI5".
