When Hanna "Ziggy" Bergstrom moves to New York City for graduate school, Will Sumner thinks his responsibilities to his best friend's nerdy little sister will be limited to the occasional dinner and check-in. Little does he know that Ziggy is ready to break out of her bookworm academic shell and move more into bombshell territory. Of course she figures the gorgeous womanizing venture capitalist Will is the best person to help mentor her in this new field of study: dating.

Will takes on the challenge with more than a healthy dose of scepticism and humour, but soon finds that Ziggy just needed a tiny push, not a world of change, to reveal a woman every man seems to notice. Soon "Ziggy" is gone and the unfiltered, innocently seductive Hanna Bergstrom is hijacking his dreams, his moods, and even his orderly no-strings-attached dating life-beginning the night his mentoring activities move between the sheets.