The Flash Season 6 Episode 15 The Exorcism of Nash Wells

As soon as Barry and his team learn the consequences of Crisis on Infinite Earths, they begin to piece together a plan for their next move. It becomes clear that Nash Wells is compromised by the dark matter and different identities residing within him. Sherloque warns that a similar phenomenon has previously caused destructive multiversal rifts, and soon enough, Nash begins to hear a voice in his head that claims to be Eobard Thawne.

Caitlin and Cecile connect with Ramsey, who they believe can help them perform an exorcism on Nash, but he refuses at first. Ramsey claims to have moved on from his prior villainous ways, but nevertheless, he has his own reasons for wanting to stop Thawne. When they finally convince him to help, they realize they need Nash to willingly release Thawne into a containment field. Nash is understandably resistant, since they would also be imprisoning those alternate Wellses he views as family.

Meanwhile, Barry and Iris try and cope with the loss of their daughter in the Crisis timeline. They confide in each other about their feelings of guilt and regret, along with the new pain that has come along with knowing that their daughter will never exist. They work together to channel their sense of loss and rekindle their partnership.

As the team works towards exorcising Thawne, they encounter several problems, including the personal struggles of each member of the team. Joe's grief for his fallen alternate universe self prevents him from being as involved as usual. Iris's growing concerns for future crises makes her feel even more distant from Barry. Allegra's insecurities about her journalistic skills and her relationship with Nash make things even harder.

In the end, the team manages to trigger the exorcism of Thawne from Nash, but the troubled Wells has to come to terms with the loss of his other selves. The containment field proves to be a better alternative to Nash's suicide run to destroy the multiverse and the team is forced to imprison Thawne to protect all realities. The episode ends on a somber note, with each member of the team grappling with the consequences of their actions and the losses they've endured.