Reviewed by Louis Rabinowitz.

Previously on The Flash: on the night of the particle accelerator explosion, Caitlin’s fiancée, Ronnie Raymond, was vaporized and seemingly killed. However, a few months later, a slightly dirtier Ronnie popped up, now sporting the ability to burst into flames (and also a terrible wig). A couple of months after that, former scientist Hartley Rathaway revealed to Cisco that Raymond had in fact merged with scientist Martin Stein, who had connections with a project with the world’s worst acronym, F.I.R.E.S.T.O.R.M…

This week’s episode, The Nuclear Man, functioned as part one of the show’s first two-parter – and as such, the show’s usual full-throttle action was dialed back a little for a more character-focused episode. The metahuman of the week, of course, was Ronnie Raymond and Martin Stein, aka Firestorm, who reappeared on the scene after accidentally deep-frying a physicist. The concept of two people trapped in the same body is a fairly wacky idea, but The Flash’s writers managed to portray the unique concept effectively enough to easily sell the idea, thanks to some spirited acting from Robbie Amell (who had the tough task of emulating Victor Garber’s mannerisms, and generally succeeded) and an extended look at Martin Stein’s home life.

Ronnie had already been glimpsed in flashbacks and has a major tie to one of the show’s regular characters, but Martin Stein hadn’t been seen before this episode – and considering that Stein was the person in control of Firestorm’s mind, it was important that we knew enough about the other half of Firestorm to care for the character once it was revealed that the character was in fact a ticking nuclear time bomb (a plot device that provided some urgency to a subplot that could have been a little leisurely in less safe hands). Stein’s backstory is fairly simple at this point – a worried wife and enough science awards to make Wells jealous – but having a first-hand look at the character’s home life added some important depth for the character that really paid off towards the end of the episode.

And while The Nuclear Man was generally light on action, the short battle between Barry and Firestorm was a fantastic scene – after the lacklustre action of the last couple of episodes, the four-colour thrills of seeing Firestorm carry Barry up into the atmosphere before dropping him back to the ground marked a return to the terrific comic-book action that The Flash specializes in. Next week may provide more Firestorm action than the sole scene here, but credit must be given to the writers for pulling off a scene that looked very ambitious on paper.

Along with Firestorm, The Nuclear Man also focused on two subplots – one a little more interesting than the other, but both with their merits. The Reverse Flash mystery has been left on the boil since the mid-season finale, but this episode return delved right back into the mystery for a set of extremely intriguing scenes. Joe and Cisco made a fun pair to watch (ironic considering the slightly morbid subject matter), and while the logic behind the ability to summon up holograms of the night Barry’s mother died was shifty (I’m admittedly not looking for scientific accuracy in a show about a man who can run at 700mph), Joe and Cisco’s investigations did provide a few very interesting answers… and yet more questions.

Most importantly, it was revealed that, courtesy of some blood left behind wallpaper, Barry was present that night as an adult. For certain comics readers (this reviewer not being one of them), this may not be a huge shock, but for the general audience, it’s a huge twist, essentially confirming that time travel is very much part of The Flash’s universe, and some day Barry will travel back in time to his mother’s murder.

The Flash has already introduced some fairly major concepts from the comics such as Speed Force, but the idea of time travel is a game-changer for the show – and to introduce it so early is a bold statement of intent from the writers. If the Reverse Flash mystery had stalled a little for a few episodes, The Nuclear Man jumpstarted it, providing a key future flashpoint for one of The Flash’s most engaging ongoing plotlines.

In subplot number two, we had Barry’s burgeoning relationship with journalist Linda Park, which went through plenty of trials and tribulations this week. The early scenes, showing Barry and Linda’s first date, were a charming way to start the episode – both funny and warmly portrayed by Grant Gustin and the engaging Malese Jow – but as the relationship became strained, so did the quality. Iris’ seemingly intentional sabotage of the relationship was an irritatingly petty moment for the character – and while Barry’s swift calling out of Iris was a welcome moment of no-nonsense and realistic writing; it remains an egregious moment for the problematic character. Likewise, the subplot’s conclusion featuring a chili pepper didn’t feel quite as funny as intended – placed in a section of the episode where the Firestorm plot was (ahem) heating up, the scene felt like an unusual slip into overly goofy and teen movie-esque territory.

As part one of a two-parter, The Nuclear Man saw the show’s first proper cliffhanger – despite the STAR Labs team’s efforts to create a splicer to separate Firestorm before the metahuman went nuclear, their attempt proved unsuccessful. As the episode ended, Firestorm went nuclear, with Barry and Caitlin barely outrunning the explosion before the show’s familiar title card flashed up. Considering a good cliffhanger is a difficult thing to execute properly without seeming abrupt, confusing or underwhelming, it’s a thrilling and appropriately large-scale (nothing quite matches a nuke for scale) final moment that puts a character we’ve got to know quite well in significant peril (because just like scale, nothing quite matches a nuke for peril).

The stinger of the week is a slightly shorter one than normal, as our old friend, General Eiling, learns of the nuclear explosion and demands Firestorm is brought to him. Eiling was an enjoyably gruff and threatening antagonist (if a little thin) back in his first appearance, so his appearance here is a welcome tease that provides a concrete antagonist for the concluding half. Next week, it’s part two of our Firestorm story, as Barry takes on General Eiling and learns a few new tricks about time travel in Fallout…

Verdict: 8.5/10

Firestorm has been teased frequently in the last few episodes, so there were high expectations for this episode – thankfully, despite a romance subplot that doesn’t always hit the mark, The Nuclear Man is a strong opener to the Firestorm two-parter.

Scene of the Episode: Fireflight – Firestorm takes Barry up into the sky for some aerial shenanigans in a fantastic fight scene.