Flash season 3 episode 16
Barry with Eddie Thawne in The Flash season 3 episode 16 pictures The CW/ Warner Bros TV

The Flash season 3's upcoming episode will feature the return of old characters like Eddie Thawne, Ronnie Raymond and Captain Cold, as Barry Allen will travel inside Speed Force to save Wally West and find clues to stop Savitar.

Episode 16, which is titled Into the Speed Force, will air this Tuesday, 14 March at 8pm EST on The CW Network. The official synopsis reads as follows:

The previous episode ended with Wally getting sucked into the Speed Force, to take Savitar's place as the Speed God makes a triumphant return. Barry will head into the Speed Force to save Wally during next week's episode, wherein he will be confronted by the ghost of his past.

A promo released shows Barry telling Iris, "I am gonna find Wally. I am going to get him back." as we see Cisco and Barry entering the Speed Force. He sees Caitlin singing lullaby to an infant, Eddie criticising him for being a "hero" and Caption Cold warning Barry of not learning lessons. Later we see

According to showrunner Andrew Kreisberg we will learn more about Speed Force mythology. He told Entertainment Weekly, "Barry makes another journey into the Speed Force and it's a very different kind of journey. Last time, in a way, it was like he went to heaven, and this time it's more like going to hell — it's more about descending deeper and deeper into levels of hell. We get a little bit more about the Speed Force mythology and speedsters' connection to it."

Actor Grant Gustin, who plays the Scarlet Speedster talks about ramifications from Barry's decision, about Wally West faster and it ended up freeing Savitar. He said, "Barry's emotions can kind of get the best of him and he can make choices that seem clear and helpful in the moment that end up having ramifications that he didn't necessarily expect. That's one of those moments."