When Heidi Wood, a woman who can't help herself from helping others, spots a teenage girl with a small baby on the platform of Chicago's train system, her heart goes out to them. Not only is it cold and raining, but the pair is obviously in need of help. Soon, Heidi has spotted the homeless teenager again, and, being the nurturing type, she feels compelled to reach out to her. That annoys her husband, Chris, and selfish 12-year-old daughter, Zoe. But Heidi ignores her husband's misgivings -- after all, he's distracted by the new girl at work, Cassidy Knudsen, a lissome blonde who always seems to be nearby when Heidi calls. So when she brings the girl, Willow, and Ruby, her baby, into their condo, it only widens the gap between Heidi and Chris.