Where the parent given minor’s custody is incarcerated, it was proper to sustain a section 387 petition alleging that previous disposition no longer provided adequate protection of the minor. The minor was a dependent child living with her father and stepmother on an extended visit at the time of father’s arrest. The department filed a 387 petition alleging that a change of placement was necessary because of father’s parole violation and new charges. The court sustained the petition, removed the minor from her father’s custody, and placed her with stepmother. The juvenile court rejected father’s request to dismiss the supplemental petition because father had already made plans for the minor to live with stepmother during the incarceration. On appeal, father challenged the sufficiency of evidence to sustain the supplemental petition, arguing that because he made an appropriate plan, and the minor would be remaining in the same home, there was insufficient evidence to support the finding that the previous disposition was no longer effective. The appellate court rejected the argument and affirmed. Whether or not father was able to make plans for the minor in the event he was unable to care for them was irrelevant to the proceedings on the supplemental petition. Substantial evidence supported the finding that the minor was at substantial risk of danger because the parent with whom she was placed was incarcerated and no longer able to care for her.