Tonight on The Flash we learn what happened to Ronnie Raymond and Dr. Martin Stein when the particle accelerator exploded altering their lives forever. The creation of Firestorm linked them both together and it's up to the team at STAR Labs to see if they can help them.
Here's the official synopsis for 'The Nuclear Man':
After Ronnie (guest star Robbie Amell) attacks a physicist (guest star Bill Dow), Barry ( Gustin) and the team realize they need to go after Caitlin’s (Danielle Panabaker) fiancé who is now a dangerous meta-human. They deduce the best way to track Ronnie is to find Dr. Martin Stein (guest star Victor Garber) who was working on a project called F.I.R.E.S.T.O.R.M. Barry struggles to balance his duties as The Flash and his with Linda Park (guest star Malese Jow), and Joe (Jesse L. Martin) enlists Cisco’s (Carlos Valdes) help to reinvestigate the murder of Nora Allen (guest star Michelle Harrison). General Eiling (Clancy Brown) returns to Central City. Glen Winter directed the written by Andrew Kreisberg & Katherine Walczak.