Mass. Gen. Laws ch. 240, § 13: Respondents upon whom service cannot be made; notice; appointing agents

Section 13. The court shall prescribe the notice to be given to non-resident respondents, to respondents whose residences are unknown, to unknown or unnamed respondents, and to any other respondents upon whom for any reason service cannot be made. If the court finds that there are respondents to be affected by the decree, who have not had actual notice of the petition, it shall appoint a disinterested person to act for them.