Here’s the 24 Season 5 prequel found on the 24 Season 4 DVD. This takes place in Chicago a year after Day 4 and six months before the events of Day 5. Chloe O’Brian meets Jack Bauer who is in hiding after having faked his death. She tells him that someone hacked into her computer files three days ago and probably realized that Jack was alive. She warns him to leave town right away. After that Jack gets into a car chase.
“HE DISAPPEARED TO PROTECT HIS SECRET
HE CHANGED HIS NAME AND STARTED A NEW LIFE
HE THOUGHT HE WAS SAFE…
THEN DAY 5 BEGAN”
Also check out a behind the special featurette Making a Scene – 24 Season 5 Prequel showing how this was created.