Within the series, it launches a storyline that focused on FBI Special Agent Don Eppes's (Rob Morrow) personal life.
Assistant US Attorney Robin Brooks (Michelle Nolden) approaches FBI Special Agent Don Eppes (Rob Morrow) at a gun range and thanks him for his help during a previous case.
When he arrives, he learns that his former girlfriend from Albuquerque, New Mexico, Bureau of Alcohol, Tobacco, Firearms, and Explosives (ATF) Agent Nikki Davis (Sandra Lindquist), was found dead, supposedly from a suicide.
Don, not believing the preliminary findings, asks Dr. Charlie Eppes (David Krumholtz), his brother and an FBI math consultant, to mathematically determine whether she was inclined to suicide.
The team learns that her husband ATF Agent Richard Davis (Matthew John Armstrong) was supposed to be in Texas but was instead in Mexico.
Charlie's use of a modified version of the Holmes-Rahe stress scale indicates that, due to her involvement in community activities and her excellent record with the ATF, Nikki Davis probably did not die by suicide.
At the Davises' house, Charlie, his friend and colleague Dr. Larry Fleinhardt (Peter MacNicol), and FBI Special Agent David Sinclair (Alimi Ballard) then attempt to match the pattern caught by microphones found around the neighborhood with the sound from Nikki Davis' service revolver.
Meanwhile, the FBI team learns that someone tipped off the biker gang under ATF investigation for a series of bank robberies involving high-powered guns.
With Charlie's analysis of the DNA found in the Davises' bedroom, the team learns that one of her own teammates, ATF Agent Rho (Eric Steinberg), was behind Nikki Davis' death.
[2] Inspired by an article about the group, Port and Andrew Black, one of the show's researchers, consulted with DNAPrint Genomics, a company which used DNA to identify suspects by their geographical origin.
[2] Show creator Nicolas Falacci's comment about the use of an acoustics test in the JFK assassination inspired Port to include one in the episode.
"[2] Also, Port and Llewellyn had written the scene where Charlie, Larry, David performed the acoustics test with Bill Nye in mind.