Factual error: At the very beginning of the episode, during Agent Wells' escape in the blue van, there is a very tall skyscraper in one shot. There aren't large skyscrapers like that in DC. Also, when she crashes the van into the Tidal Basin, where did all of the cherry trees that surround it disappear to?
Party Lines - S1-E16
Continuity mistake: Agent Wells is wearing a green jacket with a black bag. In the next shot, she is wearing an orange jacket with a red bag on her back. (00:36:50)
Factual error: In the opening scene, Abe Leonard meets with a terrorist leader in what is supposed to be Iraq. However, during their conversation, their breath can be seen, even though Iraq has a hot, dry climate. Even at night, the temperature rarely drops low enough for your breath to condensate, let alone in an urban area during daytime.
Answer: It's a recurring theme on the show. Characters come and go depending on the storyline. General Cochrane, Tyler Richmond, Abe Leonard, etc.