The PC looks after her mother's exhibition about memory and family. In some ways, this should be her magnum opus. As the PC goes around, as a very special gallery attendee more than a night guard, each painting brings up a memory centering the PC's mother, whose complexities still shape the PC's life posthumously.
To appreciate art can itself be a form of interpretation - and it is here reality-shaping, too, in the way of dreams. For a game about visual art, it doesn't itself have too much visual content, and I think that keeps the focus on the text: it is not so much the appearance of the paintings that gives them their power, but the significance to the narrator.
The horror aspect starts fairly mundane, but quickly takes on a hallucinatory quality. But what makes Night Guard / Morning Star really powerful is its emotional heart: a daughter's fractious, stubborn, evolving relationship with her mother.