Part 1 of the 5-part 'Blackout' storyline in all the Superman titles. The mysterious Mr. Z returns to Metropolis and, with the help of Professor Hamilton, succeeds in entering the darkest corners of Superman's mind. Unfortunately, a mishap leaves Z and Superman suffering from amnesia.
- Martha & Jonathan Kent, Metallo, Mr. Mxyzptlk, and Eradicator cameo flashback appearances.
- Triangle 1991 #37.
- Chronological continuation from Superman #61.
- Chronological continuation in Action Comics #671.