Visible crew/equipment: When Julie is pointing her gun at Sherry, to her rear in the top right part of the screen there is a black shiny wall panel. On this panel you can see man's reflection, who appears to be wearing headphones. His reflection is in the shot for several seconds.
Factual error: In the scene where Steven Saunders phones Tony Almeida to tell him Michelle Dessler has been captured, Steven tells Tony to open a "private web socket" to IP 2188.8.131.52. Such an IP cannot exist, the maximum value for any single number in an IP is 255, anything higher like 257 is not defined. Real websites have been mentioned in the show before such as sylviaimports.com, making this reference a bit silly. Occurs at 39:38 in the episode.
Continuity mistake: When Kim is working undercover, dressed up in Saunder's daughter's clothes, she comes out of the Ladies' toilets wearing brown trainers. As she sits down at the library computer, you see she is wearing her very high heeled shoes. A few seconds later, as she is walking between the library shelves, she is wearing brown trainers.
Continuity mistake: During the hostage exchange, there is a shot of the black man waiting for Jane Saunders to walk to him, in the background we can just see a man stood behind a car door. However, in the wider shots and when Saunders jumps out of his car, the man is not there.
Revealing mistake: Right when Jack and the prisoner are walking through what appears to be the gun room in the prison, you can see the guy who attacks them through the door. You can only see a small part of him but he is obviously waiting to enter the scene and attack. (00:14:00)
Continuity mistake: When Tony locks down Tech One from his office, the CCTV screen he's watching shows the monitors in there displaying the "locked down" message moments before they actually change to the message in the next shot within Tech One. (00:36:40)
Continuity mistake: In the teachers' lounge Jack tells Chase that the second floor is cleared. When he doesn't get an answer he realises something is wrong and runs down to the floor Chase is searching. After he's cut Chase's hand off he runs out into the hallway and into the lounge which is suddenly on the same floor Chase was on.
Other mistake: At about 5:36 Jack and Ramon are playing Russian Roulette. Right before Ramon nods to Jack indicating the bullet will be fired, we see a shot of the gun from behind revealing the next chamber to be empty. The trigger would need to be pulled two more times in order to fire the bullet. (00:29:10)
Factual error: Chase gets into surgery way too quickly. Considering the time it would take for the paramedics to reach him, stabilise him, pack his hand in ice and bring him to the ER, and then for the doctors to get him ready for surgery, sedate him and actually start operating. There is no way they would have been able to do that in the amount of time they did.
Plot hole: In the scene when Jack and Nicole isolate the Singers, Jack is informed that they've been tested on site, and the results were negative for the virus, less than 15 minutes after being isolated. However, later in the day the results take several hours to be made available, and have to be processed elsewhere, in a lab. (00:17:45)
Continuity mistake: When Michelle shoots the escaping hotel customer, her gun shows a jammed shell casing while she points her gun at him. The jammed casing wasn't there after she fired her final warning shots and disapears suddenly just before she shoots him down. (00:39:00)
Continuity mistake: In the scene where Wayne and Fox are in Sherry's house searching for the pill container, right before Sherry asks, "What's going on here?" Wayne is seen wearing latex gloves. The camera then cuts to Sherry. When it cuts back to Wayne, his gloves have magically disappeared.