Elyse is stricken with gambling fever on a business trip to Atlantic City, and while on a roll with Alex's "foolproof" blackjack system, she's oblivious to her family and job. Excited at the prospect of having his system put to the test, Alex urges his folks to "go for the gold", but Elyse insists her trip is strictly business. Finally, she's persuaded to try her hand at blackjack. Swept away on a seemingly endless winning streak, Elyse doesn't show up at the architects' convention, ignores her family's needs and casts all financial caution to the wind.
The news that their mother is pregnant sends the three Keaton kids into an angry outburst resulting in a family battle. The children react with panic and outrage at the though of having a baby around, and the Keaton household is in turmoil while Elyse tries to make them see the brighter side of the situation.
Alex is thrilled to be taking a college course taught by one of his personal heroes, Professor Ephraim Bronski, but in his eagerness to impress the teacher he gets off to a bad start and is humiliated by his idol when he fails the first class assignment.
Little Jennifer is thrilled about a visit from Scott, a former neighborhood pal she hasn't seen in five years, but her happiness at the reunion is shattered when he ignores her in favor of her older sister, Mallory.
Alex reluctantly accepts a part-time job with his father at the non-profit station, and his dad is bursting with pride to have him following in his footsteps, but Alex feels his talents are being wasted.
Mallory's enthusiasm for her part-time job at a boutique causes her school grades to slip even lower than usual and Steven and Elyse agree that she must quit work, but Alex comes up with a proposal that could resolve the situation.
Alex is teamed with long-time rival James Jarrett and assigned to work at a ""hotline"" crisis center to fulfill a course requirement, and the two end up in a crisis of their own when they get a call from a suicidal student.
While Steven and Elyse are away on vacation, the Keaton house becomes a hotel for the weekend after Mallory accidentally crashes her parents' car into a telephone pole and the kids need to raise money for auto repairs.
When his best friend, Doug, meets and falls in love with Eleanor, and decides to marry her, Alex resents the fact that someone has come between their friendship and refuses to be in the wedding.
Steven and Elyse plan a nostalgic weekend with the kids before the baby arrives, and are crushed to discover that the children are not at all interested in reminiscing about old times, they'd rather be with their friends.
Alex plays Cupid to help his shy pal Skippy get together with Jane, the girl of his dreams, but his good intentions goes awry when the girl falls for him instead.
Because of Elyse's pregnancy, the family decides to get a housekeeper, so Alex hires the lovely Karen Nicholson, a totally incompetent young lady whom the family immediately adores but Steven insists she must be fired.
Alex's chances or acceptance into a smug college fraternity are dependent upon his having a knockout date for the pledge dance and when the girl cancels he pleads with Karen, the housekeeper, to accompany him but his problems are far from resolved when they arrive at the dance.
Alex becomes involved with Donna, a young, unwed expectant mother from Elyse's natural-childbirth class but his interest in her becomes an obsession when he starts planning for her child's future and acting as if they were a real family.
Mallory is crushed when her favorite aunt dies suddenly, but her feelings of sadness turns to anger when family and friends at the funeral seem to be taking Aunt Trudy's death too lightly.
The Keaton family is transported back in time when Alex dreams he is at the Constitutional Convention at 1776, but history is off track. Steven Keaton is Thomas Jefferson and has just turned down John Adams' request to write the Declaration of Independence, so it's up to Alex to convince him to do it.
To help Steven during pledge week at his TV station, the Keatons reluctantly agree to be a part of the entertainment, but the audience gets an unexpected show when Elyse goes into labor right on camera while in the middle of a song.
Still trapped at the television station, Elyse realizes she cannot make it thru the snowstorm to the hospital and prepares to gibe birth in Steven's office. Meanwhile, stuck at home by the same storm, Steven enlists the help of Bud the plumber and his truck, and heads for the hospital, thinking Elyse will be there.
The Keaton family adjusts to life with the new baby but while everyone caters to the new arrival, Jennifer struggles with jealous feelings about not being the baby of the family anymore.
Alex and his good friend James go into business together as tutors for their fellow students at Leland. However, their competitiveness threatens to undermine their business let alone their friendship particularly when one of their students turns out to be a very attractive young lady.
With two careers, three bickering children and one demanding baby, Steven and Elyse can't seem to find any time for each other. But when they do finally take the time for a quiet evening alone, they miss all the chaos.
With the rest of the family away for the weekend, Mallory is excited about having the house to herself until she is accidentally locked in the basement with the person she'd least like to be with her adoring neighbor, Skippy.
Steven takes a nostalgic trip to his hometown following the death of his father and, with the support of Elyse and the children, tries to prepare his mother for her new life in a special two-part episode.