Dr. Douglas Brooks was Hurley's therapist at the Santa Rosa Mental Health Institute. During his sessions with Hurley, he focused on helping Hurley feel better about himself, and he helped Hurley examine his unhealthy relationship with food. He also tried to help Hurley get over the accident he believed he caused when he stepped out onto a deck full of people and it collapsed, killing two people.

Dr. Brooks believed Hurley's imaginary friend Dave was a bad influence on Hurley, and he tried to get Hurley to ignore Dave. He eventually took a photograph of Hurley and Dave together. When he later showed Hurley the photograph, showing Hurley alone, he was able to convince Hurley that Dave was imaginary. ("Dave")

Flash sideways

While supervising an outing with patients from Santa Rosa, he noticed that Libby, one of his patients, had approached a stranger, telling him she already knew him. Brooks interrupted, apologized to the man, and hastily escorted Libby out of the restaurant and back to the institute.

Hugo later showed up at Santa Rosa, asking to speak with Libby. Dr. Brooks initially refused, saying that it wasn't a good idea given Libby's mental state, but Hugo was able to bribe him with a large donation to the institute. ("Everybody Loves Hugo")