S4, E19: Booth and Brennan are on the case when shattered, pulverized human remains are found in a garbage bag at a photo shoot. When the team discovers a meteorite shard lodged in the victim’s ear, they are led to the Collar Institute of Science, a famous center for physics research in D.C. After questioning scientists at the institute, they discover the remains are those of Dr. Diane Sidman, a leading scientist and editor-in-chief of the Journal of the Collar Institute, who was also engaged to the Collar’s founder. When they discover Dr. Sidman had been working on an extremely controversial project, Brennan and Booth investigate a multitude of death threats directed at her. As the team tries to decipher the cause of her death, Booth and Brennan are on the search for the killer, but their scientific method leads them into a dangerous situation. Meanwhile, Angela’s father (guest star Gibbons) comes to town to seek revenge on Hodgins, and Sweets attempts to mediate the situation.