Christine's 8-year-old son, Ritchie has been accepted into a posh private school where Christine encounters two snooty class moms, Marly and Lindsay, who can't seem to grasp the concept that Christine actually works. Her 20-something slacker brother, Matthew, lives with her, but in a pinch, also serves as Ritchie's babysitter. On the first day at Ritchie's new school, Christine is mortified to discover that her ex-husband, Richard, with whom she gets along even better than when they were married, is dating a young, nice, impossible-to-hate woman also named Christine -- the "new" Christine.

When Christine learns that Richard and "new" Christine are enjoying an intimate relationship, she becomes determined to make her own conquests. After several failed attempts to meet eligible men, she finally runs into a guy named Stan at the grocery store. Unbeknownst to Christine, Stan is a father at Ritchie's school who is known as "Sad Dad."

Richie is dreading his first swimming lesson, until Matt decides to take him. Barb sets Christine up on a blind date.