Everyone knows Superman s major weakness: Kryptonite. But what happens when that s taken off the board, as a scientific experiment turns all the kryptonite on Earth to iron? Originally published in 1971, this story turned the Man of Steel s status quo on its head. When all Kryptonite has been destroyed, the Man of Steel is anything but invulnerable as his powers slowly begin to fade and a doppelganger Superman arrives on the scene with strange powers of its own and any contact between the two might result in the destruction of the planet! Collects Superman #233-238 and #240-242.