RCW 4.28.140: Affidavit as to unknown heirs.

Upon presenting an affidavit to the court or judge, showing to his or her satisfaction that the heirs of such deceased person are proper parties to the action, and that their names and residences cannot with use of reasonable diligence be ascertained, such court or judge may grant an order that service of the summons in such action be made on such "Unknown heirs" by publication thereof in the same manner as in actions against nonresident defendants.