Trespasses is a historical fiction novel set in Northern Ireland during the Troubles. The story's protagonist is Cushla Lavery, who lives in a small town near Belfast with her mother. Cushla teaches at a Catholic primary school and helps her brother run their family pub in the evenings. Their pub attracts all sorts of customers, including soldiers. Cushla is a quiet lady who keeps herself busy at work and cares for her alcoholic mother. Also, her family avoids involvement in religious organizations such as the IRA.
Religious strife affects everyone in the village as well, and hard feelings between Catholics and Protestants begin to surface. One evening, Cushla notices a handsome middle-aged customer Michael Agnew in the pub. Michael is fifty years old married man with kids and a Protestant. He's a barrister who defends the IRA criminals. When Cushla encounters rude customers, he helps her deal with the situation. Micheal's charming personality and intelligence draw Cushla to him. Therefore, their forbidden love affair begins.
While tensions between Catholics and Protestants rise, Cushla sympathizes with Davy McGeown, her student. She saves Davy from getting bullied by his classmates. Davy's mother is Protestant, but his father is Catholic, making his family a taboo in the village. Cushla and Gina stand up for the McGeown after Davy's father gets beaten up badly by the Protestants, and she takes Davy and his elder brother under her wings.
Meanwhile, Cushla enjoys her rendezvous with Micheal basking in the feeling of being loved, but soon she realizes the consequences of their affair. Michael is a secretive man who does not let Cushla intrude into his private life, and she isn't the only woman in his life besides his wife.
Everyone in the town becomes aware of their affair, and Cushla's family pub becomes the target of local goons after they help the Mcgeown family. In the end, Tommy murders Michael, and Cushla learns the truth about Michael's identity.
