Kristina Frye and the psychics
7 episodes of The Mentalist carry this thread, 7h in all — 2 of them are in The Red John arc.
Arc membership is derived from each episode's own title and summary text. It shows where a thread is foregrounded, not every episode it touches.
In airing order
Intent on proving a so-called psychic is a fraud - as well as a killer - Patrick arranges a séance to expose the murderer.
Romantic sparks begin to fly when Patrick Jane and supposed psychic Kristina Frye cross paths again during the CBI investigation into the murder of a charismatic head of a non-profit organization that fights human trafficking.
Patrick Jane and Kristina's first date is interrupted by a report of Red John striking again, which is discovered to be a copycat. But when Kristina reaches out to the real Red John, both she and Jane find themselves in grave danger.
When Patrick Jane faces off once again with cult leader Bret Stiles, Stiles offers Jane information regarding Red John and the missing Kristina Frye.
When the son of a former client from Jane's days as a psychic is kidnapped, Jane and the CBI team are asked to help find him. Meanwhile, Jane butts heads with his former client's new "spiritual advisor".
A young man claiming to have psychic powers offers his help to the FBI in solving a pair of murders, but when he leads them to additional victims, Jane and the team begin to suspect that he is in fact the killer they're hunting.
Jane agrees to once again pretend to be a renowned psychic and be used as bait in an attempt to lure out a serial killer and give the FBI a chance to apprehend him.