Marya Waters came into existence in the days of Ancient Sumer. However, as with all deities that have lost their followers, she now has a day job. She works with five other goddesses as a private investigator.
When a demi-god and his pregnant human wife walk into Goddess Investigations, Marya is assigned their case. It seems routine enough, a portal has opened in their house, something that's been known to happen when a human carries a demi-god baby.
When Marya goes to close the portal, she discovers that this case is anything but routine and is just the start of something much bigger, and worse, when the portal refuses to close. Instead, it creates a fountain of youth when hit with Marya's water powers. As she awaits backup, a merman escapes the portal. She realizes then that the portal leads somewhere; they'll need to chase down anything and everything that comes out of the portal while they struggle to close it.
It becomes evident that an unborn demi-god is not solely to blame for the opening of the portal which leads Marya to investigate who assisted with its opening and why.