800 year old vampire Detective Nick Knight is always feeling confused about guilt. He wants to find the good in everyone. He is ordered to transport a convicted killer to the airport so she can be sent back to the USA to face the death penalty (the wait for that is usually 30-35 years).
Knight immediately concludes that she is innocent and wrongfully convicted. He asks his boss to allow him to investigate the USA conviction, which makes no sense at all. She agrees. He is infatuated with the killer, and she escapes from his custody and kills two more times thanks to Nick.
The finale involves her attacking a former boyfriend and killing him too, while Nick stands by in shock that she is not innocent, like he presumed. Out of this debacle, Nick and Schanke should have both been suspended and fired from the force, and possibly faced criminal charges as accessories to murder.
How it ends up being just another day on the force is what makes this a "jumps the shark" episode. Knight just got ridiculous. Very lame way to treat the character. He cannot be as dumb as this. Even Schanke had to know better.