Rapa tells the story of Maite, a Civil Guard sergeant with a strong sense of duty, and Tomás, a high-school teacher in search of purpose, whose lives become entangled through two complex investigations that disrupt the quiet Surface of Galician life. When a powerful mayor is murdered, both are drawn into a case that reveals a town full of secrets and hidden motives. Later, the disappearance of a Navy officer leads Maite into the closed world of a historic military base, where silence and tradition collide with the need for truth. As Maite dives deeper into her work, Tomás wrestles with his declining health and the emptiness left by a case that gave his life unexpected meaning. Together, they face a series of moral and emotional challenges in their pursuit of justice.