In Summer 1999, small-town computer genius Megan resents the arrival of outgoing and mysterious foreign exchange student Isabella. Little does she know how her life will change by Summer 2000.

In Summer 1999, Isabella grows closer to Luke while struggling to connect with Megan. In Winter 1999, Isabella searches for justice following the disastrous Christmas party.

In Summer 1999, Megan and Isabella bond during an overnight at the Chambers' cabin. Luke tries to stand up to Brent, but ends up causing more problems for his dad. Suspicions are raised after fingerprints are found on theballoon that shot Luke.

In Summer 1999, Megan wants to be adventurous and makes fake IDs for the gang. In Winter 1999, a burst pipe leads the Landrys and Isabella to a messy night at the Chambers house. Isabella wants to help but is met with resistance from Megan.

In Summer 1999, Isabella is rocked by a surprise visit from her past. In Winter 1999, Isabella's concerns for Megan lead her to some surprising news. In Summer 2000, family loyalties are tested.

In summer 1999, sparks fly at Luke's birthday party. In winter 1999, relationships are tested as Megan becomes more distant from Luke. In summer 2000, Megan obsesses over an interesting letter she received.

In winter 1999, tensions are high on Y2K. At the New Year's Eve party, a not-so-secret conversation changes the lives of the trio forever. In summer 2000, suspicion falls on Ned after some new evidence from summer 1999 comes to light.

In summer 1999, new friendships are formed and secrets are kept as the crew approaches senior year at the annual school car wash. In winter 1999, Megan and Isabella push for answers. In summer 2000, Debbie wants to protect her daughter.

Luke examines all his relationships and worries that the pressures of being a "Chambers man" have changed him.

As timelines collide, friendships implode, new evidence emerges and the shocking truth is revealed ... in more ways than one.