She's a monster. He's a mortal. Killing each other should be easy...right?
Thousands of years after the height of Greece, shades are resurrecting into the modern day from the Greek Underworld, which means Greek mythological figures like Medusa are back.
While Hades and Persephone are scrambling to figure out why shades are resurrecting, Persephone makes a bet with her mother, Demeter-she can prove that her love story with Hades isn't a fluke. True love can be found without the direction of Aphrodite and Eros. To prove it, Hades and Persephone will create a dating app, DearHades, for the newly resurrected mortals, monsters, and demigods. If Persephone fails, her time with Hades will be cut to only a week every year. If she succeeds, she'll get to stay with him as long as she wants.
As resurrected shades adjust to the 21st century, Medusa and her Monstrously Magnificent Maidens (a knitting circle of monster friends) realize that heroes are once again trying to kill monsters. Medusa matches with blind prophet Tiresias on DearHades, but it soon comes to light that Tiresias may be aligned with the heroes, as he has been seen in a group chat with them. The monsters convince Medusa to kill Tiresias before he can kill her.
Meanwhile, the heroes tell Tiresias that gorgon blood is the answer to resurrecting shades, and killing Medusa will help them resurrect more shades, including the people they care about who are still in the Underworld. Tiresias reluctantly agrees.
On their first date, the two hit it off and fail to kill each other. As Medusa and Tiresias go on a series of comical dates while monsters on one side and heroes on the other attempt to help them kill the other, Aphrodite decides to meddle with DearHades, angry that Hades and Persephone are encroaching on her territory. The gods squabble and take sides, and of course Zeus makes multiple profiles in the name of "research."
Medusa and Tiresias decide to work together and try to find the gorgon blood in the Underworld so they can resurrect people. Meanwhile, DearHades is hacked and Hera and Aphrodite encourage everyone to draw battle lines between monsters and mortals. Mortals are offered the resurrection of their loved ones for killing the monsters, and cursed monsters are offered a return to mortal forms if they win against the heroes.
Medusa and Tiresias find Hades and Persephone in the Underworld and inform them of the upcoming war. There actually is no more gorgon blood, so no one else is coming back; all the promises from the other gods are lies. Hades and Persephone go to Thanatos for help while Medusa and Tiresias return to the mortal realm and attempt to save their respective sides.
With the help of friends, Medusa and Tiresias unravel how the gods are playing them against one another, and with the help of Hades, Persephone, and Thanatos, the war is stopped and the monster-slaying heroes are defeated. Despite having tried to kill each other multiple times, Medusa and Tiresias start over. Persephone wins the bet against her mother (and makes some peace with her) as Medusa and Tiresias prove unlikely pairings can work, ending the book with a proposal several months later.