Washington Revised Code Title 4. Civil Procedure § 4.28.150. Title of cause--Unknown claimants--Service by publication

In any action brought to determine any adverse claim, estate, lien, or interest in real property, or to quiet title to real property, the plaintiff may include as a defendant in such action, and insert in the title thereof, in addition to the names of such persons or parties as appear of record to have, and other persons or parties who are known to have, some title, claim, estate, lien, or interest in the lands in controversy, the following, viz.: “Also all other persons or parties unknown claiming any right, title, estate, lien, or interest in the real estate described in the complaint herein.” And service of summons may be had upon all such unknown persons or parties defendant by publication as provided by law in case of nonresident defendants.