Family Ties - Season 5 Episode 7 : Mrs. Wrong (2) 1989

Alex sees Mallory and Nick leaving the Keaton residence in the predawn hours to elope, and unable to stop them, follows them to New Jersey where he finds the young couple taking a hard look at their decision. After Nick bumbles around the outside of the house with a 16-foot ladder, Alex makes a desperate attempt to keep his younger sister Mallory from marrying Nick. But they are too much in love to listen. It takes Erin and Mike, another couple, to give them perspective on their maturity.