Forever Knight Season 3 Episode 7 Hearts of Darkness

When a stripper wakes to discover the man she picked up at The Raven has been stabbed to death, even a polygraph test cannot spark her memory of how she got into his apartment. A lack of blood at the murder scene leads to the discovery of a vampire bite on the victim. Nick and Tracy must now search for the killer without revealing to each other their knowledge of vampires. The investigation takes a bizarre twist when their suspect exhibits multiple personalities, only one of which is a vampire, with the other two personalities operating as true mortals.