Action Comics #349 April 1967

Superman faces a frightening new enemy when Dr. Kane, a criminal scientist working with the secret organization Intercrime, transforms himself into a living source of Green Kryptonite radiation.

Calling himself Dr. Kryptonite, Kane gains the ability to emit deadly kryptonite rays, making him an especially dangerous opponent for the Man of Steel.

After capturing Krypto, Superman's faithful super-dog, Dr. Kryptonite uses him as bait to lure Superman into a trap. With both Superman and Krypto in danger, the Man of Steel must find a way to overcome an enemy whose powers are specifically designed to exploit his greatest weakness.

The issue also includes a Supergirl backup story, "Supergirl's Black Deeds!", in which mysterious aliens manipulate Linda Danvers into performing seemingly wicked acts as part of a strange game.