In Season 1 Episode 19, Joe and Cisco are on a trip to Starling City (remember "Arrow"?) to investigate the accident that claimed Tess Morgan's life and forever changed Dr. Harrison Wells.

While in Starling City, the duo had an interesting conversation with Quentin who spoke of his inability to forgive Laurel for her lies. While this conversation was on, Joe got bothered about the lies he had told Iris his daughter about the secret identity of Barry Allen.

Somewhere in the Central City, in one of the banks, an employee stole from someone's deposit box despite the clear view of the security camera. She even denied her act at the police department.

A man also tried to sell stolen diamonds at a jewellery store, though the clerk realized this and alerts the authorities, he was still able to escape. This meant Eddy had a meta human on the run- A criminal named Hannibal Bates was stealing people's identities by transforming his DNA to theirs and committing crimes. He could become just anyone he wished to.

As they had a meta human to track down, they also had an investigation concerning Harrison Wells and this was to be kept from him. Bates was causing confusion in the Central City as he was taking different forms and outsmarting Barry and Eddy.

Bates disguised himself as his grandmother when Barry and Eddy traced him to her house. When they realized this, they put up a chase but Barry could not catch up with him. Eddie nearly did but at Bates' touch, he looked like Eddy and immediately shot two police officers to death on video. Barry in his bid to have Eddy cleared, worked so hard until bates showed up at his door as a policeman and stole his identity.

Caitlin came to Barry (not knowing Bates had taken his form), with a serum that could stop Bates and took him to S.T.A.R Lab. He kisses her and she was into it until Iris arrives with a video clip to prove that the policemen were shot by a left handed while Eddy is right handed.

Before Bates could take more lives, Dr. Wells saved the day by tasing him. But he still outsmarted them by taking the form of a kidnapped little girl and tricked some construction workers to free her.

In Starling City, at the accident site, Joe and Cisco discover a corpse after digging for a while. This turned out to be the real Harrison Wells thereby proving that he was being impersonated.

Barry rushes to the airport to stop Bates who was trying to escape but he still outsmarted him and took the form of Caitlin. In the fight which ensued, Barry got an upper hand and injected him with the serum.