After gaining unprecedented access to confidential files, investigators find a cypher that may hold the key to the Zodiac Killer's identity, as well as a link between the murderer and an unsolved cold case.

The team find clues that the killer may have been in the US Armed Forces, as the supercomputer pinpoints symbols in the code that only a scarce few could have known.

The team locates a curious new cipher associated with the Zodiac Killer, while the supercomputer identifies an odd lunar pattern that connects the killings. Plus, a riddle left by the killer may reveal the location of a body.

The hunt reaches high-gear as the FBI releases secret files on the mysterious Zodiac Killer, and a handwriting analyst connects the Zodiac's letters to a taunting letter mailed 3000 miles away in Albany, New York.

The Code Team announce that a team member has solved the zodiac's infamous Z340 code, which has eluded codebreakers for 50 years.