Of all the new characters "The Flash" has introduced in Season 2 -- and there have been a lot -- nothing could shake up S.T.A.R. Labs as much as the return of Dr. Harrison Wells (Tom Cavanaugh). Earth 2 has opened the door to a lot of wacky possibilities, but it would be safe to say that an alternate universe Wells was the last person Barry Allen (Grant Gustin) would have expected to save him from King Shark in episode 4. Now the Flash must decide if he trusts his mentor-turned-murderer's doppelganger in episode 5, "The Darkness and the Light." 

The episode begins with a trip back -- or is it forward? -- in time to Earth 2. There, Wells is in the middle of a press conference announcing speedster-detecting smartwatches when he is interrupted by the Jay Garrick version of the Flash. Garrick accuses Wells of creating the meta-humans and, thus, unleashing Zoom (Tony Todd) on the world. Wells denies it and insists Garrick should focus on his job -- stopping Zoom. 

After the opening credits, the show returns to Barry's world, where he is tasked with reintroducing Caitlin (Danielle Panabaker) and Cisco (Carlos Valdes) to the man who blew up their lives. Naturally, they grill this much sassier Wells. Tom Cavanaugh appears to be having a ball putting this snarky spin on the familiar character. 

"I'm guessing you didn't travel across dimensions just to meet the Flash," says Barry.

"That's exactly what I did," Wells responds. It turns out he wants to help Barry stop Zoom. "Zoom has infected my world, and now he has come for yours."

Wells also has a confession about Zoom. "I created him," Wells admits.

Joe (Jesse Martin) crashes the party and is not happy to see Wells. In fact, he fires three shots at the scientist. Barry has to snap into action to catch the bullets. And he has to pull Joe aside to set him straight. 

"This is a lot take in, but that guy is not Wells," Barry tells his cop father figure in the teaser video. "Eddie [Rick Cosnett] erased that Wells from existence. This guy is someone else."

That is not to say that Barry is without worry.

"You think this is easy for me?" Barry asks. "The guy in there looks, moves, sounds, exactly like the guy that drove a knife through my mother's heart. I'm trying to get past this."

Joe tries to trust Barry ... and Wells, but later he gives Iris (Candice Patton) a gun, just to be safe. That is a paranoid move for the usually level-headed cop. 

Meanwhile, Barry and Cisco go to clear their heads at the coffee shop where Patty (Shantel VanSanten) makes a move on Barry. He blows it, though. He is too overwhelmed by the Wells situation. Cisco tries to "show Barry how it's done" with a cute cashier, but he gets turned down. However, that triggers one of his visions where he sees a new meta-human, Dr. Light (Malese Jow), robbing a bank. He tells Barry, and the Flash is off like lightning!

Barry misses Dr. Light and returns to S.T.A.R. Labs to debrief with the rest of the team. There, Garrick and Wells have as much trouble agreeing in this world as they did in Earth 2. Garrick thinks that Dr. Light can be reasoned with, but Wells insists she has been sent by Zoom to kill him. 

Barry goes with Garrick's plan and confronts Dr. Light at her next score. She agrees to talk, but when she takes her mask off, Barry recognizes the meta-human. It's Linda Park! Apparently, Barry's ex is one of Zoom's cronies. When Dr. Light realizes Barry knows her identity, she gets spooked. She flashes him with a blast of light that leaves him temporarily blind. 

Back at S.T.A.R. Labs, Wells is worried that Dr. Light will try to kill her Earth 1 doppelganger -- Linda. Garrick does not agree and goes with Caitlin to keep an eye on the journalist. Barry, on the other hand, still has no vision. That is a problem. Earlier he had worked up the courage to ask Patty out, and he knows he can not cancel on her now. 

With the help of Cisco, Barry shows up at his now-literal blind date sporting some nifty black sunglasses and a mic in his ear. For a few minutes "The Flash" becomes a screwball romantic comedy. But eventually, Patty catches on and Barry gets out of jail with some excuse about having come from getting his pupils dilated. The date goes swimmingly all the same. It even ends with a kiss so hot it restores Barry's vision. 

He needs it too, because then Dr. Light ambushes Garrick and Caitlin at the Tribune and tries to kill Linda Park. She fails, but only because Iris is there to save the day with that gun Joe had fortuitously given her earlier. The attack does leave the paper's editor dead, though, and Barry realizes he has to start giving some credit to Wells, who brutally lays into Garrick back at the lab for being a coward. Barry gives Wells Dr. Light's mask -- she lost it in the attack -- in the hopes that it will help in tracking her down.

Wells knows just what to do. Barry might have dismissed how Cisco knew about Dr. Light's first attack, but Wells knows the truth. Thanks to that smartwatch of his, he proves that Cisco is a meta-human and he thinks Cisco can make use of Light's mask. The S.T.A.R. Labs team is shocked that Cisco has been keeping such a big secret, but there is no time to quibble about it. They have to find Light. 

Cisco touches the mask, but nothing happens. Wells says Cisco's fear is just getting in the way -- a theme that has come up a few times in the episode, even on Barry's date. Wells presses Cisco to try again and again before finally shoving the mask into his chest -- eerily similar to way in which the old Wells put his fist through Cisco's chest to kill him. It works. Cisco gets a vision of Dr. Light at the train station. Barry rushes to the scene and takes down Dr. Light before she skips town. 

Afterwards, Barry tells the S.T.A.R. Labs team that he plans on going after Zoom, not laying in wait. Wells is pleased, but Garrick warns Barry that he's not ready to take on Zoom alone. Barry counters that he is not alone. He has everybody at S.T.A.R. Labs with him, including Garry. However, Garrick says he cannot stick around to just to see Barry get killed. He is leaving. 

Meanwhile, Barry, Cisco, and Caitlin meet up at the coffee shop. Cisco gets another shot at that cashier -- Kendra Saunders (Ciara Renee), aka Hawkgirl -- and this time he gets a number. Plus, Caitlin and Barry decide he needs a meta-human and Barry anoints him Vibe. 

It will be the last scene of the episode, though, that will leave fans with the most questions. In a cut-away to Earth 2, Zoom makes an appearance where he is keeping a mysterious girl prisoner. It's Jessie Quick (Violett Beane). The short conversation between Jessie and the villain suggests that Wells is Quick's father, at least metaphorically, but viewers don't get any answers just yet. Fans will have to wait for episode 6 to find out. After episode 5, perhaps the series' strongest hour yet, that is going to feel like a long wait.