The Flash 4×22 “Think Fast” Season 4 Episode 22 Inside – DAVID RAMSEY GUEST STARS — When DeVoe assaults an A.R.G.U.S. facility to complete his Enlightenment Machine, Barry (Grant Gustin) realizes the only way he can stop him is if he allows Cisco (Carlos Valdes) and Caitlin (Danielle Panabaker) to accompany him into the facility. Still shaken by Ralph’s death, Barry isn’t sure he wants to risk any more of his friends’ lives and considers taking on DeVoe solo. Viet Nguyen directed the episode written by Sam Chalsen & Kristen Kim (#422). Original airdate 5/15/2018.