It looks like there will be flashbacks and alternate realities in the 20th episode of The Flash.
In the episode, Barry (Grant Gustin), Caitlin (Danielle Panabaker), Cisco (Carlos Valdes) and Joe (Jesse L. Martin) set a trap for Wells (Tom Cavanagh). Cisco uses himself as prey which puts him in grave danger. Meanwhile, Eddie (Rick Cosnett) makes a decision regarding Iris (Candice Patton), which leaves Joe a bit unsettled.
Here are some new promotional images released by The CW today. BIG spoilers in the photos, to say the least. The episode airs on April 28.