During a mission, Hobbes takes a serious fall when Darien gets sloppy. He is sent to the hospital with a homeless patient named Sarah. Suffering from memory loss, Bobby wanders into a surgery theater and witnesses a strange experiment. He forgets that when the guards knock him out. He is then sent for surgery on short notice. Darien finds him and he seems completely cured. However, Sarah has disappeared. They investigate and find her on streets, in poor mental conditions. It turns out she and other homeless people have been used for experiments involving Schwann cells used for regenerative cerebral functions. Darien and Hobbes return to the hospital, and force him to return the transplanted cells in storage to the original "donors". However, there are none left for Sarah. The doctor flees only to take a fall like Bobby's and suffer brain damage. The Keeper is able to duplicate the surgery and uses the brain dead doctor's Schwann cells to restore Sarah to normal.