Think Fast

"Think Fast" is the twenty-second episode of the fourth season of The Flash, and the ninety-first overall. It aired on May 15, 2018.

Synopsis
When DeVoe assaults an A.R.G.U.S. facility to complete his Enlightenment Machine, Barry realizes the only way he can stop him is if he allows Cisco and Caitlin 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.

Trivia

 * This will be the penultimate episode of The Flash Season 4.
 * Diggle's extreme susceptibility to motion sickness is once again witnessed, with Caitlin and Cisco preparing a trash can for his inevitable bout of vomiting following Barry superspeeding him into S.T.A.R. Labs.
 * The episode referenced the last break in to an A.R.G.U.S facility from Infantino Street.