It's hard to believe that in its 51-year history, "Doctor Who" has never done a Robin Hood episode. That's all about to change, though.

The September 6 episode is titled "Robots in Sherwood," and it's exactly what it sounds like. There was no historical Robin Hood that resembles the myths and legends we tell about him today, so how could "Doctor Who" do an episode about the character? By making that myth the mystery the episode revolves around.

"Robots in Sherwood" was written by Mark Gatiss, who seems to have a penchant for classics and legends. Along with "Doctor Who" showrunner Steven Moffat, Gatiss co-created "Sherlock."

Here's BBC America's official plot description:

In a sun dappled Sherwood forest, the Doctor discovers an evil plan from beyond the stars, and strikes up an unlikely alliance with Robin Hood. With all of Nottingham at stake, the Doctor must decide who is real and who is fake. Can impossible heroes actually exist? Tom Riley (Da Vinci’s Demons) and Ben Miller (Death in Paradise, Primeval) guest star.

You can take a look at a trailer for the episode below, along with a slideshow of images for "Robots in Sherwood" above.