Hannah Wells is an FBI agent who investigated the terrorist attack that killed President Richmond and every other person present at the State of the Union address, ever since Scott Wheeler, her love interest, was one of the casualties. Under Tom Kirkman's authority, she became the lead investigator into the conspiracy.
During the events of the first season, Hannah was the one to eventually find that Peter MacLeish, the survivor of the Capitol bombing, was hiding in a bomb shelter beneath the Capitol and that he was involved with the conspirators responsible. She also discovered the identity of another conspirator, named Catalan. Ultimately, she was able to expose the conspirators who dubbed themselves as the True Believers and thus led to their downfall.
A few moments after the Capitol explosion, Hannah made an attempt to call a close friend named Scott Wheeler but was sent to voicemail. After seeing the plumes of smoke rising from the Capitol in the distance, Hannah got in her car and drove to the flaming wreckage. While the FBI and emergency services dig through the rubble, they find an explosive commonly found in the Middle East, but was later deemed dysfunctional. From that point, most of the team suspected major terrorist groups in the Middle East, but Hannah became skeptical. She theorized that whoever perpetrated the bombing was just getting started.