Episode 4.16 of The Mentalist will be called "His Thoughts Were Red Thoughts". Written by Jordan Harper.
The episode features the murder of a man in his late 20s to early 30s. He was a good guy and an anti-cultist who we will see in a flashback or two, showing his fatal attack.
Among the cult are (ex-)police officers, politicians, an attorney, college students and even the sister of the victim who is left seemingly cold by the awful news. They hold their meeting in what they call "Serenity Center".
The producers are also looking for two alive anti-cultists - a former cultist and old hippie in his late 50s and a good-natured man in his 30s who is devastated when his close friend is murdered.
Source: Spoiler TV.