A More Permanent Hell - S2-E20
Revealing mistake: Mt. Vesuvius is erupting and LaCroix's villa is collapsing around him. But while the ground "shakes," statuary falls over and the walls cave in, look closely at the fountain/pool in the center of the room. There's not a drop splashing out of it. In fact, the water's surface is smooth as glass.
Continuity mistake: In the flashback, the level of whiskey in the bottle changes from 1/3 empty to nearly full and back again as the shots alternate. (00:16:25)
Curiouser & Curiouser - S2-E22
Revealing mistake: After Nick demands to be told what's going on, LaCroix leaves - but his reflection remains in the mirror for a few seconds after we hear the sound effect of his flying away. (00:28:45)
Near Death - S2-E23
Continuity mistake: While Nick is interviewing Dr. Linsman, the position of his hands shifts (from lying flat on the desk to held up near his face) every time the camera angle changes. (00:08:15)
Near Death - S2-E23
Continuity mistake: The flashbacks here recount Nick's "bringing across." But for the second time in the series, the recap of this event contradicts the original pilot film version in that the characters have all changed costumes. (00:25:10)
Near Death - S2-E23
Plot hole: Dr. Linsman puts a heart monitor on Nick for the experiment, but for some bizarre reason, never questions why her "patient" has a resting heart rate of only one beat every ten minutes.
Revealing mistake: At the episode's end, the sharp, moving background of nighttime Toronto from the top of the CN Tower suddenly shifts to a still, blurry (and glaringly obvious) matte image. The scene was partly shot atop the actual tower, but because high winds and sway made the location too dangerous, it was abandoned, and the bulk of the scene had to be shot in studio and processed. (00:37:15)
Close Call - S2-E25
Continuity mistake: Though the camera angle doesn't change, the brightly lit Chinese-character sign on the wall outside the window moves several feet to the right between takes. (00:09:10)
Close Call - S2-E25
Continuity mistake: In the establishing shot of the epilogue, it's 9:10 on the clock outside the station. But in the very next shot, it's 7:10 on the clock inside. (00:42:20)
Crazy Love - S2-E26
Factual error: Dr. Shawna Welsh's medical degree, visible on the office wall behind her while she talks to Nick, misspells the name of Johns Hopkins Medical College as "John Hopkins." (00:08:35)
Crazy Love - S2-E26
Continuity mistake: The flashbacks here contradict series canon. Nick's victim, Amaya, is shown to have been bitten (by him) several times. In every other instance, unless he had multiple captive ladies to "sip" from, Nick's bite was fatal in one go. In fact, it was a major recurring plot point that Nick "couldn't stop."
Answer: Nick was sick and tired of being an immortal bloodsucker. He wanted to be human, fall in love, get married, have children, grow old and die. As for Janette, according to her, she fell in love and the passion she felt "cured" her of her blood lust.