In tales that ushered in the new millennium, Superman returns to Smallville and teams up with Superboy! Plus, The Joker and Harley Quinn invade Metropolis! And in "Critical Condition," Superman must search for a missing Lois Lane while a mystery illness threatens his life! Collects Superman #155-159, Adventures of Superman #577-581, Action Comics #764-768, and Superman: The Man of Steel #99-103.