Factual error: In the episode where Sydney is supposed to be in Helsinki, there are visible skyscrapers in the background. There are no skyscrapers in Helsinki.

Continuity: Emily Sloane's left ring finger was shipped to Arvin Sloane in one episode in Season 2, when they are reunited in the Philippines, the left ring finger is bandaged and missing. Later, in the episode when she is shot, when she tells Arvin the CIA is listening, the left ring finger is there.

Continuity: "Season premiere, Authorized Personnel Only, part 1." When Sydney and the other agent are in the bathroom at the club, Sydney begins to smear black dirt on the agent's tee shirt for his punk transformation. The first smears that she applied differ when he exits the bathroom.

Revealing: In episode 3x10, Remnants, when Lazare shows up to talk to Will, we see that his left hand has been cut off. When Lazare is about to leave, he has his hands at his sides, and we can see that both arms are the same length, but the left one should be shorter, because it has no hand.

Continuity: In Season 3, Episode 11 "Full Disclosure", when Sydney is torching the lab you see 6 test tubes labelled with her name shatter and spill. In the next shot the tubes are back on the rack and intact.

Other: Season 4: Episode 3- "The Awful Truth" Near the end of the show they are supposed to be in a parking garage in Spain, but there are way too many American cars.

Plot hole: "Unveiled", episode 3x18. Vaughan discovers Lauren is a mole when he goes through her briefcase and discovers the wig, gun and fake passport she used in Germany a few hours before - surely even the worst secret agent in the world would have enough sense to get rid of such incriminating evidence as soon as possible, and not carry it back to the USA (sneaking it onto a plane, presumably) and leaving it in the room where the man you're lying to sleeps. Lauren is a highly skilled agent, if the Covenant selected her for a mission this important, so it's out of character (without an explanation) for her to be so sloppy.