The story follows Corona who is on a journey of self-discovery as she follows the pages of her late father's journal. With an LED device she built that extends over her head, the light it casts prevents Shadows from reaching her as she travels at night to avoid other survivors. She eventually has a run-in with other survivors who believe the Light is what will save the lost souls (Shadows), who are now wandering the night, through rebirth. They call themselves the 'Daymarks', a term for a lighthouse, which is where they've built their new city around.
Some important symbolism. Corona got her name from her father based on the corona around the moon during a solar eclipse. She was the only light in the darkest times of his life where the corona is the only light left during an eclipse. The dreamcatcher is a memento from her mother that had died during childbirth.