Susan Bailey is the sister of Gordon Bailey, Valerie's ex-husband.
Susan was diagnosed with multiple sclerosis right after starting a new job. She enlisted the services of Anderson/Vaughan Investigations when she believed a trial she'd participated in had poisoned her and the other participants, leaving them blind and paralyzed temporarily.
They investigated the situation and decided to go after the raw data from the first round of the trial to see if any of those patients had had the same kind of symptoms. Sophie and Danny attended a presentation he was giving and Sophie hacked into his laptop to get the data. However, the published data and the raw data were the same, making them wondering what happened in the second trial that got such a different outcome. They found Cathy Green, a nurse who had previously worked for the competition. In order to find out if she was the saboteur, Alice went under cover as a patient and the rest of the team used the security cameras to guide Alice through the facility so she wouldn't get caught. Nurse Green started an IV on her, but Alice managed to stop the flow before any of the medicine entered her body. Once Green was gone, she pulled the IV out and took the drug with her. She handed it off to Danny and Valerie for testing. The results came back negative and Alice realized it wasn't the drug that had poisoned them, but the juice the participants were given after infusion. It was laced with belladonna. Dr. Watkins tanked the trial because the drug wasn't working and he wanted to start work on another drug in order to help his wife, who also had MS. This information gave the trial participants a case.
She is very close with her brother and ex-sister-in-law. Even after the divorce, Valerie declared that she'd do what it took to help Susan.
She interviewed for and got a job at Edgewick Capital after "Christopher" made a call.