My inspiration for this came from a dream I had.
My character, Lafayette Belmont, is an antique collector and hunter. He tracks down rare and priceless objects for the rich and wealthy. After arriving back from Egypt for a special client of his, he returns home to find a mysterious woman (Your character) awaiting his return at his mansion. She pretty must let herself in. Lafayette humors her after a while and listens to her request. There has always been myths about Werewolves, the children of the Moon Goddess and what not. Well your character has some map of sorts a family member left behind years before she was born. When she discovers it she begins to do research on it and her search puts her here, with Lafayette. Lafe reads the map and takes note of symbols he had seen in several other places in his journey that mentions a Goddess of the Moon and a Divine Tear. Lafe has the resources to fish out more of this curious map and has no choice but to bring your character along. Their trip brings them to the Big Apple, and even several locations across sea until they reach ancient Ruins left behind by 'Children of the Moon'.
Now this will be mature as Lafayette is a womanizer, an alcoholic and a heavy smoker. He loves using bad language too. So what I'm looking for in your character is perhaps a strong woman who is not intimidated by Lafe. Now I don't want her to push Lafayette around either like a bully. Hopefully this makes sense. I haven't decided the time line yet but perhaps not modern. *shrugs*