The Nuclear Man

"The Nuclear Man" is the thirteenth episode of the first season of The Flash, and the thirteenth episode overall. It aired February 10, 2015.

Synopsis
After Ronnie attacks a physicist, Barry and the team realize they need to go after Caitlin's fiancé who is now a dangerous meta-human. They deduce the best way to track Ronnie is to find Dr. Martin Stein 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 relationship with Linda Park, and Joe enlists Cisco's help to reinvestigate the murder of Nora Allen. General Eiling returns to Central City.

Behind the scenes

 * The episode's title is a reference to the debut issue of Firestorm, Firestorm - The Nuclear Man.
 * When he encounters Firestorm outside the Steins' house, Barry asks him not to "flame on." This phrase is utilized by Johnny Storm/the Human Torch, a Marvel Comics character with similar powers to The Flash 's Firestorm, when activating his powers.
 * When Barry mentions his plan for their second date to Linda, he mentions "Mal Duncan, who's playing at an underground jazz club". In the DC comics, Malcolm "Mal" Duncan was one of DC's first black superheroes, Hornblower, who could play a horn which opened up multi-dimensional portals. During his time spent with The Teen Titans, Mal Duncan owned a nightclub which was frequented by his team mates.
 * Harrison Wells mentions the the "Firestorm Matrix" inside Ronnie and Professor Stein. In the DC comics, the Firestorm Matrix is an established plot point with in-depth details as to how the Firestorm persona works, similar to the Speed Force with speedsters.