735 ILCS 5/2-203.1
If service upon an individual defendant is impractical under items (1) and (2) of subsection (a) of Section 2-203, the plaintiff may move, without notice, that the court enter an order directing a comparable method of service. The motion shall be accompanied with an affidavit stating the nature and extent of the investigation made to determine the whereabouts of the defendant and the reasons why service is impractical under items (1) and (2) of subsection (a) of Section 2-203, including a specific statement showing that a diligent inquiry as to the location of the individual defendant was made and reasonable efforts to make service have been unsuccessful. The court may order service to be made in any manner consistent with due process.
735 ILCS 5/2-203.1