Day 4: 10:00 P.M.-11:00 P.M. - S4-E16
Continuity mistake: When Jack shoots Nicole through the wall, she slides down, smearing blood on the wall. However when Jack comes to check if she is dead, no blood is seen on the wall.
Day 4: 11:00 P.M.-12:00 A.M. - S4-E17
Continuity mistake: When Jason and his wife are trying to escape from Marwan, they run through a corridor filled with water puddles. A few seconds later, one of Marwan's men goes through the same corridor to follow them, but none of the puddles had any ripples, which they should have considering the amount of water and time elapsed.
Day 4: 11:00 P.M.-12:00 A.M. - S4-E17
Continuity mistake: When Jack gets out of the helicopter near the reserve power station, he slams the helicopter door, but it immediately bounces back open. In the next shot its closed.
Day 4: 12:00 A.M.-1:00 A.M. - S4-E18
Factual error: In the opening scene of the episode, Marwan gives a cohort Lat/Long coordinates for a nuclear missile. The computer shows these coordinates as being in the Midwest, they are actually in Nevada. (37 14' N 115 21' W).
Day 4: 12:00 A.M.-1:00 A.M. - S4-E18
Continuity mistake: To get crucial information from Prado, Jack offers his resignation to Buchanan, and takes Prado on as a private citizen. But Jack doesn't work for CTU; he works for DOD, and is at CTU on a provisional basis.
Day 4: 1:00 A.M.-2:00 A.M. - S4-E19
Plot hole: At 01:50 am, Chloe is told to go to Sabir's house. She arrives there approximately 5 minutes later, at 01:55:45. At 01:58, Jack is told that the closest tactical team is 15 minutes away from Sabir's residence. A few moments later, Jack mentions that the tactical team is 10 minutes apart from Chloe, meaning they bothered to send the team over there even though any officer currently at CTU HQ, including Jack, could get over there a lot sooner.
Day 4: 1:00 A.M.-2:00 A.M. - S4-E19
Continuity mistake: At the very end of Episode 18, Jack knocks out Joe Prado after breaking his thumb and getting information from him. At the very beginning of Episode 19, we see Prado already being treated for his injuries, with a hand splint, and nurses checking his head, within the CTU clinic. Even if you factor in the opening recap sequence at the beginning of every episode, that means that Joe Prado regained consciousness, Jack unhooked his handcuffs, and dragged him back to CTU in three minutes or less.
Day 4: 4:00 A.M.-5:00 A.M. - S4-E22
Other mistake: After Michelle and Tony kiss, he goes away and she says 'Tony, be careful'. In the next episode in the "previously on 24" section Michelle whispers it to his ear. (00:29:30)
Day 4: 5:00 A.M.-6:00 A.M. - S4-E23
Continuity mistake: In the first scene where we see Tony as a hostage, Mandy comes over to him and he has a white gag in his mouth, which is taut. Mandy says, "Is she gonna do the same for you?" and the camera cuts back to Tony, whose gag is now limp on both sides.
Chosen answer: Nobody knew, not even the writers, until at least halfway through the season when they were writing the end. They wanted to keep all options open.
Nick N.