Prison Break actor Robert Knepper will reprise the role of William Tockman aka The Clock King in the seventh episode of The Flash.
Knepper first played The Clock King in the Arrow season two episode 'Time Of Death'.
"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."
says Producer Andrew Kreisberg.
Robert Knepper is well know as playing Theodore 'T-Bag' Bagwell in Prison Break alongside Wentworth Miller, who has also joined The Flash cast this season as Leonard Snart aka Captain Cold.
The Flash will air on The CW on October 7.
(Source: TV Line)