If you specifically meant Season 7, Episode 3, the "piece" of evidence crucial to that case involves:
The team has to piece together his military background and the specific trigger of a car accident to stop his mass murder spree at an internet security company. "Criminal Minds" The Fisher King: Part 1 (TV Episode 2006)
A man suffering from Capgras Syndrome (believing his loved ones have been replaced by imposters) after a traumatic brain injury. [S7E3] The Fisher King
The "piece" for the puzzle was a section of a large map or picture that, when assembled, revealed the location of his "Grail"—his daughter, Rebecca.
In this storyline, the Fisher King lures the team into a "quest" for the Holy Grail by sending them individual clues or physical items. If you specifically meant Season 7, Episode 3,
In the context of the popular crime drama Criminal Minds , the "piece" usually refers to the physical puzzle pieces sent by the unsub Randall Garner—the Fisher King—to the BAU team.
Each team member receives a personal item or message while on vacation that leads them back to Virginia. In this storyline, the Fisher King lures the
However, the episode titled is actually the two-part finale of Season 1 (Episode 22) and the premiere of Season 2 (Episode 1). If you are looking for Season 7, Episode 3 , that episode is titled " Dorado Falls " . The Puzzle Pieces in " The Fisher King " (S1E22 / S2E1)