Plot

Bob Russell (Garrett M. Brown), his wife Cindy (Elaine Bromka), and their three kids, 8-year old Miles (Macaulay Culkin), 6-year old Maizy (Gaby Hoffman) and 15-year-old Tia (Jean Kelly), recently moved from Indianapolis to Chicago. Tia resents her parents because she feels everyone was happy enough where they were already living.

Bob and Cindy are in bed one night when Cindy's aunt calls, telling them that Cindy's father has had a heart attack. Bob and Cindy immediately make plans to go to leave for Indianapolis. Upon being told the news, Tia angrily states that "If my whole family moved away from me, I'd have a heart attack too", and slams the door in her mother's face.

Despite trying everyone they know, the are unable to find a sitter for the kids. Bob suggests his brother, Buck, despite Cindy's objections.
Cindy and Bob leave for Indianapolis, leaving 'Uncle Buck' in charge. Buck does the best he can; Miles and Maizy come to love him, but he must repeatedly assert his authority over the rebellious Tia. He is also dealing with constant pressure of commitment from Chanice Kobolowski (Amy Madigan), his girlfriend for the past eight years.

Buck meets Tia's boyfriend, Bug (Jay Underwood), and instantly realizes that he is clearly only interested in sex with her. When Buck scares Bug away from her with a hatchet he claimed he wanted to show him (proclaiming to be so proficient with the weapon he's been known to "circumcise a gnat"), an infuriated Tia gets revenge by making Chanice think that Buck is flirting with the Russells' neighbor, Marcie Dahlgren-Frost (Laurie Metcalf). Chanice leaves Buck.

Tia escapes the overprotective Buck, sneaking out to a house party to see Bug. While there she realizes that Bug is only interested in her for sex, which he tries to pressure her into. Buck finds his way to the house and barges in on Bug by drilling through the doorknob, only to discover that not only has Tia already left (having turned Bug down), but Bug is already with another girl.

Buck starts driving back home, finding Tia wandering by herself on the streets. In the car, Tia admits that Buck was right about Bug all along: Buck stops the car in a quiet area and opens the trunk, revealing a tied up Bug. Buck requests that Bug apologizes to Tia with subtle threats of drilling his teeth out, and then lets him go (while still tied up). Bug then yells various obscenities and threatens to sue as he retreats, prompting Buck to remove his golf clubs and drive a ball into Bug's head. Bug continues screaming obscenities, in obvious pain, until Buck drops yet another ball, ready to swing, as Bug disappears into the night.

Buck has finally earned Tia's love and respect, so back home she admits to Chanice that she set Buck up to look like he was flirting with Marcie. Chanice reunites with Buck.

Later, Cindy and Bob return home as Cindy's father is recovering. Tia meets her mother as she enters the house. Cindy is expecting a loud tirade. Instead, she is surprised to receive a tearful embrace. Cindy promises that things will change, so Tia won't be so resentful of her parents any longer. Uncle Buck leaves with Chanice as the family waves goodbye.