Very pregnant and not quite married, Jenny Harris doesn't mind that she and her live-in fiancé, Dean, accidentally started their family a little earlier than planned. But Dean is acting distant, and the night he runs out for cigarettes and doesn't come back, he demotes himself from future husband to sperm donor. And the very next day, Jenny goes into labor.

In the months that follow, Jenny plunges into a life she never single motherhood. At least with the sleep deprivation, sore boobs, and fits of crying (both hers and the baby's), there's not much time to dwell on her broken heart. And things are looking Jenny learns how to do everything one-handed, makes friends in a mommy group, and even gets to know a handsome, helpful neighbor. But Dean is never far from Jenny's thoughts or, it turns out, her doorstep, and in the end she must choose between the old life she thought she wanted and the new life she's been lucky to find.