Polyamory on The Mentalist was approached better than on the Bones episode, discussed over on another thread.
The Mentalist, Season 2, Episode 16, "Code Red"
A woman scientist is poisoned. Among many suspects are the victim's husband, her lover, and a former lover of her husband. In the end, none of them had anything at all to do with the murder. Their relationships had nothing at all to do with the motive.
The agents observe the victim and both her partners all interacting with each before her death. It was interesting watching the assumptions and their deflation.
It felt great to have the evidence lead elsewhere and the poly situation be just another red herring. It felt like a bit of education and a bit of being treated like "normal."
It felt wonderful.