"What was that?" Cisco cried.

"There's been an unidentified energy impulse in the generator," Caitlyn said. "Barry, don't go down there until I have a better idea of what it is."

"What if it's dangerous?" Barry protested. "I should at least check it out."

"No, Barry," said Doctor Wells. "Stay here." Barry would have tried to protest, but he was interrupted by a red and white blur, which skidded to a stop and resolved into a teenage boy in a skintight suit. "I think we found your unknown impulse, Caitlyn," the doctor noted.

"Impulse," said the boy. "That's so crash! Catchy, dramatic, one word—"

"How did you get in here?" Caitlyn asked, cutting him off.

The boy shrugged. "Time machine, tour of the past, got a little off course. Do you know how to get to Mount Justice from here?"

"Where?" asked Barry. The boy whirled around and hugged him.

"Grandpa Barry!" he cried. "I've dreamed about doing this – when you weren't so old and I didn't have to worry about breaking you. This is so crash!"

"Who are you?" Caitlyn asked. The boy released Barry and ran up to her.

"Question is, who are you? You don't look like anyone from Dad's old photos. Neither do you two. Where are we, anyway?"

"This is STAR labs," Doctor Wells told him, a calculating glint in his eye. "I'm Doctor Harrison Wells, she's Caitlyn Snow, and—"

"Whoa, Killer Frost? Am I interrupting a kidnapping or something?" He tugged on Caitlyn's hair. "Is this a disguise?" She yelped. "Guess not. What's going on, Grandpa Barry?"

"We're a team," said Barry. "And you still haven't told us who you are."

"Right! I'm Bart Allen, aka Impulse, your grandson from the future. Ta da!" They stared at him. "You can do a DNA test if you want. Does the League exist yet?" He was met by a trio of blank looks and a single calculating gaze. "Guess not. Who else is around? Superman? Wonder Woman? Martian Manhunter? Batman? Anyone? I'm not the best at history, but even I know you weren't the first one, Grandpa."

"Are you talking about vigilantes?" asked Cisco. "Like the Arrow in Starling?"

"Green Arrow? Oliver Queen? He wasn't even a founder! And what's Starling? GA was from Star City, everyone knows that. Are there any other metas around?"

"Too many," Caitlyn muttered.

Cisco counted them off on his fingers. "So far, we've encountered Weather Wizard, Multiplex, the Mist, and Barry, but we're pretty sure there's more." Caitlyn rolled her eyes at his insistence on naming the supervillains.

"Really?" asked Bart. "This is so moding. Is Jay Garrick around anywhere?"

"Who?"

Bart sighed overdramatically. "Definitely the wrong universe. So feeling the mode here." He ran back out of the lab, Barry following a second later. The boy ran to a small gray capsule, examined it, stuck his head inside, and cried, "There it is!" He gave Barry another quick hug, climbed into the capsule, and cried, "Bye, Grandpa Barry!" The capsule vanished in a display of energy, and the others found Barry staring at empty space.

A few weeks later, Caitlyn found a test tube labeled "Impulse" and filled with blood. She didn't tell Barry when the paternity test came back positive.