Finn, a century-old red fox who takes human form for fun, steals a stranger's heirloom ring—and accidentally breaks it. Unable to pay it back, he offers himself instead, and somehow ends up married to him. Finn believes his husband is an ordinary human, so he hides his fox ears and tail; Adrian, meanwhile, is secretly a black snake—also an immortal—and thinks Finn is human too. Two monsters, both hiding their true nature, learn how to be a human couple. Over decades, they secretly dye their hair white, paint on wrinkles, and dread facing their partner's death. Only after nearly two hundred years do they discover: the "mortal" each feared losing was just like them—and can stay by their side for a very, very long time.
