A case takes a personal turn for Carrie when she and Al investigate the apparent murder of Dr. Eugene Lustig, a prominent researcher in the field of human memory. Some years back, Lustig had helped bring Carrie out of a dark place in her life by using her in a study with other individuals that shared her unique memory. She and Al question Lustig's assistant, Alwyn Pierce, who had a history of conflict with some of the study members, but the mystery deepens when Pierce is found strangled to death. As they investigate Pierce's death, Carrie uncovers an assortment of tapes from Lustig's original study, with one specific date missing. She theorizes that one of the group members lied about a memory on that tape in order to cover something else up, and then proceeded to kill Pierce after she started snooping around. Carrie goes to talk to the other living members of the study, including Dale Pringle, who gradually becomes the prime suspect. By utilizing Carrie's memory of the study events, Lustig's teachings about the impacts of adrenaline on their memories, and police records of unsolved murder cases, the team discovers that Pringle not only killed Lustig and Pierce, but four others as well. As he explains to Carrie, the adrenaline rush the murders provided him gave him an escape from the endless burden of his powerful memory.