The Flash,
Season: 1
Episode: 17
Time: Tuesday 8/7c
Air Date: March 31, 2015
Channel: CW
“Trickster”—A copycat killer known as the Trickster sets off bombs in Central City. In an effort to stop him, Barry and Joe seek help from the original Trickster (Mark Hamill), a criminal mastermind who has been imprisoned for 20 years. Meanwhile, Iris asks Eddie to help with a case. In flashbacks, Harrison Wells is shown coming up with the idea for the particle accelerator.