Joel Barish (JIM CARREY) and Clementine Kruczynski (KATE WINSLET) are a classic example of opposites being attracted to one another. He's reserved and pensive, while she's an outgoing and impulsive free spirit. Despite some good times together, it isn't surprising when they begin to have problems with their relationship.
Little did Joel know, however, how far Clementine would go to end it. With the help of Dr. Howard Mierzwiak (TOM WILKINSON) and his team at Lacuna, she's set out to have Joel completely and permanently erased from her memories.
When Joel realizes what she's done, he makes an appointment with Lacuna receptionist Mary (KIRSTEN DUNST) and then awaits technicians Patrick (ELIJAH WOOD) and Stan (MARK RUFFALO) to work their memory magic and have Clementine removed from his.
In the middle of the process, however, Joel realizes he's again enjoying his time with Clementine - if only in his memories - and wants to stop it. Yet, since he's unconscious, his only recourse is to flee within his own head - accompanied by a now sentient, memory-based version of Clementine - and try to avoid the erasure team that's coming after the two of them.