Md. Code, Tax-Prop. § 14-837
When an owner cannot be ascertained as provided in § 14-836 of this subtitle, the unknown owner of the property may be included as a defendant by the following designation: "Unknown owner of property ..... (giving a description of the property in substantially the same form as the description that appears on the Collector's certificate of tax sale), the unknown owner's heirs, devisees, and personal representatives and their or any of their heirs, devisees, executors, administrators, grantees, assigns, or successors in right, title and interest," and the unknown owner shall be so designated throughout the proceeding, and the cause shall proceed against the unknown owner by publication under order of the court as provided in this subtitle.
Md. Code, TP § 14-837