Subject 9

"Subject 9" is the fourteenth episode of the fourth season of The Flash, and the eighty-third episode overall. It aired on February 27, 2018.

Synopsis
Barry meets a powerful woman whose abilities could help him in his battle with DeVoe. Meanwhile, after learning that DeVoe is targeting everyone who was on the bus, Ralph decides he doesn’t want to be a hero anymore, his only concern is staying alive. Harry offers to help Joe.

Trivia

 * This episode is in reference to the TV show, Fringe, Season 4, episode 4, "Subject 9" in which the team must look for the subject of an experiment which gave him superpowers. Since the Bus Metas are each referred to by Devoe as Subject and a number based on their order, and eight Bus Metas had been identified prior to this episode, the title is likely indicative of the next Bus Meta.
 * In the DC comics, there was a supervillain who went by the name, The Fiddler Isaac Bowin. Here it's seen that Miranda MacDougall's character Izzy Bowin is the genderbent version of him although it's yet to be determined if she'll have villainous roots similar to two characters of similar origin.
 * This is the second episode of season 4, and of the show, where Joe West does not appear, but he is mentioned by Cecile when talking to Harry Wells.