Mother, a single parent, left two children, ages seven and three, alone in a hotel room when she went to work. At the time of the twelve month review hearing, the parties stipulated that there was a substantial probability the children could be returned, and a therapist opined that mother had learned proper parenting skills and would not leave the children alone again. However, mother tested positive for marijuana several times, though she was never diagnosed as having a substance abuse problem. The trial court terminated services and set a 366.26 hearing. The appellate court here granted mother’s 39.1B writ, holding that substantial evidence did not support the finding that returning the children to mother would create a substantial risk of detriment to the children. Mother substantially complied with her reunification plan, and had 84 drug-free tests in comparison to the five positive marijuana tests. She was not required to demonstrate perfect compliance. Mother did not leave the children unattended and had made substantial progress in court-ordered programs. She was employed, and there was no concern expressed regarding her living conditions. The social worker said her parenting skills were improving. There was no testimony linking mother’s alcohol and marijuana use to her parenting judgment or skills. Therefore, the juvenile court was directed to return the children unless evidence of detriment was shown at a new section 366.22 hearing.