After Barry was brought out of the Speed Force and they defeated Girder, that was around the time that Oliver showed up at STAR labs.
"Looks like I missed quite a party." Oliver said.
"You have no idea man. But, there was one positive." Barry said as he showed off his speed.
"You got your powers back." Oliver said.
"He's not the only one with powers." Laurel said.
"What do you mean?" Oliver asked.
"When I was fighting Girder in front of the West House, he yanked my sonic device off my neck and crushed it like it was a piece of bread. He was about to kill me, but suddenly, I screamed it was like my device had somehow been implanted into my throat, since my scream was even more powerful." Laurel said.
"Wait, you're a meta?" Oliver asked.
"She must've been affected by the dark matter explosion that sent Barry into the speed force like Thea and Jesse were." Cisco said.
"So, why did I get an actual canary cry instead of being put in a coma?" Laurel asked.
"You and Thea were both wearing your suits during the explosion and that included your sonic device. The dark matter was must've bonded the device into your DNA, allowing you to have a canary cry without the need of a device." Cisco postulated.
"Okay, so, that answers that, but now onto my sister." Oliver said, looking at Barry pointedly.
"I think I can help with that. Come on." Barry said as he led the 2 of them over to the medbay.
"Allen, you should be resting. You don't need to be here." Harry said.
"No, actually I think I do." Barry said as he first took Thea's hand in his own and they noticed a bit of electricity surge from his body into her body and immediately, Thea's eyes opened and Barry then proceeded to do the same thing with Jesse.
"How did you do that?" Oliver asked Barry, amazed yet again by Barry's powers.
"Are you, like, magic now?" Cisco asked.
"Did you know that was gonna happen?" Laurel asked.
"Maybe. It's hard to explain." Barry said.
"It's It's the Speed Force." Harry said and Barry nodded.
"I feel strange." Thea said.
"Strange how?" Barry asked, though he had his suspicions.
"I feel kind of awesome, like everything is buzzing, electric, like I could do anything." Thea said, confirming Barry's suspicions.
"Thea, would you mind using the treadmill real quickly. I think I know what's going on with you, but I want to be sure before I say anything." Barry said and Thea nodded, confused, as she got out of bed and walked out.
Barry was about to follow when Oliver stopped him.
"You think she has powers?" He asked.
"Not just any powers. Come on, if I'm right, you'll see." Barry said and Oliver nodded as they headed over to where Barry's treadmill was.
"Okay Thea, we're just going to keep gradually increasing the speed, you just try and keep up." Barry said and Thea nodded as she began running at normal speed with the treadmill, at least, until the speed cranked up.
Thea started panting as she struggled to keep up, but the speed just kept increasing to the point that she wasn't even sure how she was still on it, until she turned her head to see bright yellow lightning emanating from her body.
"That confirms it." Barry said as the treadmill came to a sudden stop and Thea sped into a padded wall.
"Ow." Thea groaned as Barry helped her up.
"You're a speedster now." Oliver said to his sister.
"I guess Speedy really was an appropriate nickname after all." Thea joked.
"Oliver, while I think Laurel can learn to use her powers in Star City, I think that it would be best if Thea stayed here for now so I can teach her how to use her speed." Barry said.
"Agreed." Oliver said.
"I was expecting a bit more of a fight." Barry admitted.
"Barry, I've seen what you can do. Having that sort of power on my team will make a huge difference in our fight, but only if Thea knows how to use it properly. It's best for everyone if she learns how to use her powers from the scarlet speedster himself." Oliver explained.
"I'm ready to go home now though. I have a score settle with Darhk now." Laurel said.
"Get in line. Darhk is mine to kill. Especially after what I just went through in Hub City." Oliver said.
"Why were you in Hub City?" Thea asked.
"I got in contact with Constantine and he got me touch with someone who could teach me how to resist Darhk's magic. Let's just hope it worked." Oliver said.
"I'm gonna head back to my mom's and pack up and then we can head back to Star City." Laurel said and Oliver nodded.
"I just hope John hasn't done anything too stupid while we were gone." Oliver said.
"Why?" Thea asked.
"The reason Nyssa died is because Andy double crossed us. He gave Darhk the missing piece of the idol, which he stole from the bunker, with assistance from Merlyn, who I still regret not killing when I had the chance, and John blames himself. Hell, he even tried to kill Darhk's wife last week." Oliver said.
"Wow, and to think out of all of us, he's one the who had the least interactions with Nyssa." Thea said.
"She was still a friend and teammate. It took me and Lyla a lot to talk him off that ledge." Oliver said.