On May 19, 1921, Nelson posed as a plumber to enter the residence at 1519 Pacific Avenue in San Francisco and attempted to molest 12-year-old resident Mary Summers in the basement. His attempt was thwarted when she screamed and attracted help from her elder brother. Nelson fled, but was captured hours later while riding a trolley. At a competency hearing, he was deemed dangerous and recommitted to Napa State Mental Hospital. He would escape again on two occasions before being discharged from the institution in 1925.