It’s The Flash‘s midseason finale. After two decades of being haunted by the memory of his mother’s murder, Barry Allen finally meets her killer, the episode’s titular speedster. But that’s far from the only game-changing moment in this week’s episode.

It’s Christmastime in Central City. And Barry and Iris exchange gifts. He gives her a replica of her mother’s wedding band, while she gives him… a microscope. Well, it’s the thought that counts. But Iris receives an even bigger gift from Eddie — the key to his home. They’ve been dating a year now, and he wants her to move in. Candice Patton has the first of several nicely understated moments in this episode when Iris — upon being handed a jewelry box by her suitor — allows a look of worry to pass for just a moment across her face, as though deep inside she’s not sure the two truly belong together. But she’s relieved to learn Eddie’s merely interested in cohabitation at this point.

Caitlin, meanwhile, is having problems with her own would-be boyfriend. She briefly encounters long-thought-deceased fiance Robbie, still looking like a grunge rock performer after his reintroduction last episode.

At Mercury Labs (named after the Roman god of speed, natch), the man in the yellow suit arrives and kills several security guards, prompting Dr. Wells and Barry to pay a visit to the company’s Dr. Tina McGee. In order to catch the yellow blur, they need a tachyon device she’s created. Spurred by the thought of finally catching his mother’s killer, Barry is uncharacteristically ruthless, and ultimately secures the machine by threatening to spill Mercury’s secrets to the press. Here, Grant Gustin proves his turn as “Bad Flash” in last week’s “The Flash vs. Arrow” was no fluke, and again shows he can portray an SOB when the situation calls for it.

Barry’s taken down a peg, however, when he learns he’s finally losing the love of his life. Iris tells him she’s moving in with Eddie, and it’s torture to watch the heartbroken hero fight to maintain a brave face. To complicate matters, she adds that Eddie believes Barry has romantic feelings for her. Which the young police scientist denies of course. Gustin again excels here, marking the multiple wounds Barry suffers throughout the exchange.

The “Opposite Flash” (Cisco’s still working on a name) then appears, and leads Barry to a sports stadium, where they battle at super-speed. It’s another uniquely done, first-rate action sequence, with the camera following their chase across the halls, bleachers, and field, each punch landing with a quick burst of lightning. Winning this first round, Barry’s opponent tells him it’s his destiny to lose to him, and his mother’s destiny to die.

Caitlin and Cisco go into full Ghostbusters mode and track down Ronnie with their PKE meter. He insists he’s not who they say he is, and mutters the word “Firestorm” before bursting into flames. Caitlin later tells Cisco she’s worried they’ll have to cage Ronnie with the criminal metahumans they’ve captured.

Wells and Joe tell Barry to leave while S.T.A.R. installs the tachyon device, so he visits his father in prison and confesses he failed to stop the man in the yellow suit. Barry’s dad tries to cheer him up, and reveals he knows he’s in love with Iris, thus officially making Iris the only person on the show who does not know this.

Fortunately, she’s not made to look clueless very long, since Barry immediately visits her and tells her of his long-held feelings. With scarcely any dialogue, Patton again finds solid footing in Iris’ reaction. She almost makes us forget this is the third or fourth time this episode that someone has cried.

With Central City PD standing by, S.T.A.R. captures the yellow blur. But he breaks free, beats Wells, attacks the police, and again brings out the Flash. Their fight this time is brief, and it looks like Barry’s about to be destroyed when he’s saved at the last second… by Firestorm. Ronnie flies off into the night sky, leaving Wells to promise Caitlin they’ll “bring him home.”

Barry admits to Joe he lost to the man in the yellow suit because he’s feared him his whole life. Joe offers him some holiday cheer by taking him home to find his friends — including Iris and Eddie, whom Barry congratulates — gathered around their Christmas tree.

We’re left with two revelations — Cisco tells Joe they’ve discovered that a man in a red suit was also present the night of Mrs. Allen’s murder; and Wells has the yellow speedster’s suit, which he fits with the stolen tachyon device, in his secret lair at S.T.A.R. “Merry Christmas,” says the scientist, in the voice of the Reverse Flash…

“The Man in the Yellow Suit” makes good on just about all the promise the season has built up thus far. It gives us a solid look at the danger a truly destructive version of the Flash could pose, even if we’re still left with plenty of questions about his origin and motives. Is Wells really the evil speedster? If so, why has he so carefully protected Barry this season, even killing some who would harm his protege? And just who was that second speedster the night of his mom’s murder?

It’s a testament to The Flash‘s writing that the exchanges between characters, of which there are aplenty in this episode, are almost as interesting as the action sequences. For all the meaningful moments, heart-to-heart conversations, and high levels of sentimentality, the show somehow doesn’t cloy or suffocate under the weight of its emotions. That’s due in large part to executive producer Greg Berlanti, an admitted sentimentalist and unabashed fan of Frank Capra movies, who recognizes that meat tastes even better when served with a side of corn. Berlanti and fellow producer Andrew Kreisberg clearly love these characters, and they’ve managed to make us love them almost as much in just ten episodes.

Accelerated Particles

— DC comic heroes are distinguished from Marvel’s by their legacies. Several generations of Flashes, for example, have ran through the DCU. The DC TV Universe smartly follows suit in recognizing the value of lineage. Smallville featured guest turns by many actors from various screen Superman productions. While The Flash has utilized both lead actors from the character’s 1990 TV show — John Wesley Shipp, as Barry’s dad, and now Amanda Pays, who again plays a scientist named Tina McGee.

— The Reverse Flash, like so many of Barry’s greatest foes, was created by writer John Broome and artist Carmine Infantino. He was introduced in September 1963’s Flash #163.

— This is the second time in as many episodes where Cisco’s belief in the need for a cold gun, should a speedster ever go bad, has been justified. If Wells is the Reverse Flash, could his anger at Cisco for losing the weapon (in “Going Rogue”) be motivated out of fear for his own alter ego’s welfare?

Next: The Flash takes a well-deserved holiday break, but returns January 20th for the “Revenge of the Rogues”!

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What did you think of this week’s episode? Let me know in the comments below or on Twitter (@JMaCabre).