We already know about the crossover coming up between Arrow and The Flash, but another reminder of the shared universe is going to happen in episode seven of the new CW series (according to TVline). Robert Knepper will be reprising his role as William Tockman / The Clock King, but this time he'll be facing the Scarlet Speedster instead of the Emerald Archer… and he won't be alone.
Executive producer Andrew Kreisberg said: "We wanted to give Barry a real challenge… TWO bad guys! Barry will be fighting both a new enemy and one of our scariest and most successful Arrow villains in The Clock King."
Who the new villain is remains a mystery at this time.