Maggie (Hathaway) is an alluring free spirit who won't let anyone - or anything - tie her down. But she meets her match in Jamie (Gyllenhaal), whose relentless and nearly infallible charm serve him well with the ladies and in the cutthroat world of pharmaceutical sales. Maggie and Jamie's evolving relationship takes them both by surprise, as they find themselves under the influence of the ultimate drug: love.