Jeremy Fink is about to turn 13. In just one month he will officially become a teenager and enter into teendom.

A package is delivered in the mail for Jeremy. It is an unusual, engraved wooden box about the size of a shoebox. Engraved on the box is the inscription - "The Meaning of Life: For Jeremy Fink to open on his 13th birthday." Jeremy recognizes his dad's handiwork on the box and realizes it is from his father, who died five years earlier. There are four different locks on the box that require four different keys to unlock them. Unfortunately the keys have been lost. Jeremy has one month to figure out how to open the box in time for his 13th birthday.

Jeremy, along with his best friend, Lizzy, begins searching for the keys needed to open the box. After breaking into the office of the attorney they believed mailed the box to Jeremy, they find themselves doing community service for Mr. Oswald.

Jeremy and Lizzie are delivering packages for Mr. Oswald. Through these experiences Jeremy has meetings with the selected people Mr. Owald sends him to. He begins to learn the meaning of life on his own. He begins the journey from childhood into adulthood.