Last time, in the first part of this double episode, I told the story of the disguise-wearing, letter-writing serial killer operating in California’s Bay Area in 1968 and 69, who christened himself Zodiac. His choice of victim changed, as did his MO, so how do you catch a killer whose only motive is achieving infamy and mocking the police? Join me for Part 2, where we’ll analyse the killer’s behaviour and review some of the popular suspects and theories, and we’ll hear from Zodiac expert Michael Butterfield. It’s a case that’s now over 50 years old, so will the killer ever be named?