Revealing mistake: When Natalie shows Nick the murdered museum guard's bite wounds in the morgue, the "dead" man's carotid artery is pulsing quite healthily. (00:08:30)
Factual error: The murderer works for a blood bank and drives a bloodmobile, a plot holdover from the first pilot ("Nick Knight"), which was set in Los Angeles. This second pilot, however, is set in Toronto - and Canada doesn't have mobile blood units. (00:31:35)
Dark Knight: The Second Chapter (2) - S1-E3
Continuity mistake: The blood stains on Nick's white turtleneck are lighter, then darker, then lighter again, and migrate to different positions, both during his fight with LaCroix in the abattoir, and throughout the hospital scenes afterward. (00:10:15 - 00:19:30)
Visible crew/equipment: When the parish priest is preparing for the Easter Pageant and gathers up the bundle of sticks, the microphone dips into the shot at the top of the screen. (Aired version only. Mistake was digitally removed on the dvd.) (00:16:05)
Continuity mistake: While he's in the confessional, Schanke's raincoat collar is turned up. When he rushes out to confront Nick, it's folded neatly down again. (00:37:40)
Factual error: The murder victims, all Catholic, are specifically said to have "all worn crucifixes." But the jewelry Nat hands Nick as evidence, the cross that burns his hand and the necklace Magda later gives him are all plain crosses, not crucifixes. (The former is unadorned; the latter has a Christ figure on it.)
Factual error: Vampire Erica commits suicide by sitting on a park bench at sunrise. Nick and Schanke are called to the scene only a short time later, or so we're led to believe, yet it's still fully dark when they arrive. No sunrise in sight. (00:01:00 - 00:05:30)
Factual error: The doll that supposedly belonged to Erica 300 years ago is too obviously modern, with a plastic head and body and nylon hair.
Continuity mistake: Schanke calls Nick to tell him they've found Mrs. Hedges' body, and says, "They cut her throat, man." We even see a brief shot of the bloodied corpse. But later in the morgue, Nick says, "She was asphyxiated, right?" and Nat agrees. The corpse on the autopsy table now appears to have an intact throat. So, which way did Mrs. Hedges die? (00:22:15 - 00:38:10)
Dance By The Light Of The Moon - S1-E7
Revealing mistake: The flashbacks to 1228 in this episode portray some of the same events - Janette seducing Nick, LaCroix making Nick a vampire - that are also shown in "Dark Knight." But here, Nick, Janette and LaCroix are all wearing completely different costumes.
Continuity mistake: When Nick breaks into the old Chinese herbalist's warehouse, he twists and breaks a doorknob lock. But when he walks through to the inside, there's a latch-and-bar array instead of a knob. It's a completely different door.
Continuity mistake: Elizabeth the leper is wearing a dirty gray dress under her black cloak - until Nick makes her a vampire, when suddenly there's a beautiful, spotlessly clean white gown under her cloak. (00:09:30 - 00:26:30)
Character mistake: Nick asks Janette if she's ever turned anyone else into a vampire - an odd question, considering the fact that he already knows she has. He was there when she brought the baroness across in the 18th Century flashback sequence for "If Looks Could Kill." It's even odder that Janette tells him she's never done it, since she knows that Nick knows she has. Apparently, the only one not in the know here was the scriptwriter.
Continuity mistake: Nick's beard is fully grown in the beginning of this episode, but it changes, disappearing entirely more than once and then reappearing in various stages of growth, even in sequences supposedly occurring on the same night.
Plot hole: Near the end, a cop comes to tell Schanke that an explosion has been reported at Nick's place. But neither of the two intruders uses any explosives. One shoots his way in through a door and the other breaks in through a skylight. Neither makes enough noise for the disturbance to be called an explosion. (00:41:15)
Plot hole: When the two henchmen who break into Nick's loft to kill Lisa are captured, the case is closed. But the two thugs were reporting back to a boss who wasn't caught, and who surely would have sent more hitmen after Lisa. So the case shouldn't have been closed.
Plot hole: Nat thinks Nick is becoming more human because he can see himself in the mirror, and he replies, "Only sometimes." This line contradicts series canon, as "Forever Knight" did not adhere to the vampires-don't-appear-in-mirrors cliché. Nick was seen to reflect very nicely, in fact, every time he passed a mirror, and not just "sometimes."
Spin Doctor - S1-E15
Continuity mistake: Nick takes to the air wearing a blue windbreaker, but lands wearing a long black duster coat. (00:14:05)
Spin Doctor - S1-E15
Factual error: Nick tells Nat about his past life as an assistant professor in the U.S., and refers to himself as "a certain indigenous vampire." Nick wasn't indigenous (native) to either the US or Canada, where the show was set. He came from Brabant, now part of Belgium. They were probably trying for "itinerant" (wandering), which would accurately describe Nick's long life.
Plot hole: Nick calls Schanke and asks him to take the Polaroids in to a lab for analysis. But Nick seems to have forgotten that he has the photos with him. They're not back at the precinct station for Schanke to take them in. (00:30:25)
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.