As a child Barry Allen witnessed his mother's murder. He become an assistant police forensic investigator to get answers about her death.
After the S.T.A.R. Labs' particle accelerator explosion left him in a coma, Barry was revived 9 months later with superhuman speed.
While the S.T.A.R. Labs team studies Barry's new abilities, he fights crime as The Flash protecting Central City from other metahumans. The particle accelerator accident affected many people and not all of them use their new abilities for good.
Captain Cold: Make the plan. Execute the plan.
[King Shark appears]
Barry: Expect the plan to go off the rails.
Barry: I love you, Iris.
Iris: Oh. I love you, too.
Barry: When we were kids I loved you before I even know what the word love meant and then my mom died and I had to go live with the girl I had a crush on. Look. There were so many times I wanted to tell you; Jr. Prom, when I went away to college, when I came back from college, nights that we stayed up talking, all the birthdays, all the Christmases, but I, I never did. I kept it in. After I lost my mom and my dad, I was afraid that if you didn't feel the same way, I would lose you, too. That's the irony. I was so scared of losing you that I did. I know I've had our whole lives to tell you this and you're with Eddie now and I know that and I know my timing couldn't be any worse, but I just... I couldn't lie to you anymore. I'm sorry.