The Devil's Greatest Trick

"The Devil's Greatest Trick" is the thirteenth episode of the sixth season of Arrow and the one-hundred-twenty-eighth episode overall.

Synopsis
Cayden James discovers a secret about Green Arrow that pushes him over the edge. Knowing everyone and everything he loves is in danger, Oliver must decide if he can do this alone or if he needs to turn to his old teammates for help. William starts to demand more of Oliver's time.

Trivia

 * Barry Allen makes a cameo in this episode. Oliver has Barry rush Oliver and John to meet Cayden James before he leaves the city.