Are you watching Season 2, or was this a different show with a similar name?
It seems you are referring to a specific episode from the CBS series Instinct . Based on your description of a "solid story" and it being Episode 7, you are likely talking about the installment, titled " After Hours " . In this episode:
What part of the story did you find the most solid (the murder mystery or the subplot with the serial killer)?
Chipped nail polish found in an alley points to a hotel concierge, revealing a motive involving debt and resentment towards wealthy clients.
Dylan (played by Alan Cumming) and Lizzie (Bojana Novakovic) go undercover, noted for their strong performances.
Instinct Review: After Hours/Go Figure (Season 2 Episodes 7-8)