Skulduggery Pleasant: Dark Days is a young adult and fantasy novel written by Irish playwright Derek Landy, published in April 2010. It is the fourth of the Skulduggery Pleasant series and sequel to Skulduggery Pleasant: The Faceless Ones. The story follows sorcerer and detective Valkyrie Cain as she attempts to track down the original head of her mentor Skulduggery Pleasant to rescue him from the world of the Faceless Ones. A team of previously significant villains returns, joining forces to get their revenge upon the pair. The book did not see release in the US and Canada until 2018. HarperCollins Audio also publishes the unabridged CD sets of the books read by Rupert Degas. Source: Wikipedia (en)