Wash. Rev. Code § 4.28.160
All such unknown heirs of deceased persons, and all such unknown persons or parties, so served by publication as in RCW 4.28.150, provided, shall have the same rights as are provided by law in case of all other defendants upon whom service is made by publication, and the action shall proceed against such unknown heirs, or unknown persons or parties, in the same manner as against defendants, who are named, upon whom service is made by publication, and with like effect; and any such unknown heirs or unknown persons or parties who have or claim any right, estate, lien, or interest in the said real property in controversy, at the time of the commencement of the action, duly served as aforesaid, shall be bound and concluded by the judgment in such action, if the same is in favor of the plaintiff therein as effectually as if the action was brought against such defendant by his or her name and constructive service of summons obtained: PROVIDED, HOWEVER, That such judgment shall not bind such unknown heirs, or unknown persons or parties, defendant, unless the plaintiff shall file a notice of lis pendens in the office of the auditor of each county in which said real estate is located, in the manner provided by law, before commencing the publication of said summons.
RCW 4.28.160