Hindsight

"Hindsight" is the ninth Christmas episode of the NBC series ER, aired in the show's ninth season.

Synopsis
The past 24 hours play in reverse after Luka gets into a car accident with Erin. Luka was forced into working hungover after a staff Christmas party, leading to a patient being brain-dead. At the party, he confesses to Abby that he misses her before an oblivious Carter interrupts.