"Three Ghosts," the ninth episode of Arrow's second season, has just had some of its details laid bare, courtesy executive producer Marc Guggenheim's Twitter feed. The episode is based on a story by executive producers Greg Berlanti and Andrew Kreisberg, who are showrunning The Flash spinoff, with a script by DC Entertainment's Chief Creative Officer Geoff Johns and Arrow writer Ben Sokolowski. It's to be directed by John Behring, with shooting having just started, according to Guggenheim's tweet. Green Arrow TV confirms that Barry Allen (The Flash) will make an appearance in the episode. "Three Ghosts" should air sometime in December, depending upon scheduling.