Still, the question marks and dashes make a clear image: a picture of an insect with wings spread open. It’s just a little bit creepy, especially if you’re old enough to remember the poster campaign for The Silence of the Lambs: the moth spread over Jodie Foster’s mouth. On closer examination, though, this isn’t a moth but a cicada, and it’s the emblem of some of the most convoluted and taxing puzzles ever created. The puzzles are set by a group called Cicada 3301, which resurfaced via a post on Twitter in January — to the delight and frustration of millions — to bamboozle the world for the third year in a row. The Cicada 3301 puzzle — more a chain of interlinked puzzles drawn from a wide variety of disciplines — purports to be a recruitment tool, though no one knows for what. It could be the CIA, MI6 or the NSA (or none of these). Past solutions have embraced William Blake, transposition ciphers, Mayan numerology, The Mabinogion, Aleister Crowley, number theory and Carl Jung. They cross media boundaries, require visits to physical locations (mostly but not exclusively in the US) as well as the more obscure reaches of the internet, and no one has ever — publicly, at least — claimed to be responsible or worked out who is. Speculation is rife, wild, paranoid and infinitely varied. The truth may be out there, but it is remarkably well-hidden.