Challengers of the Unknown #68

Challengers of the Unknown #68 (On Sale: April 1, 1969) has a cover by Neal Adams.

"One of Us is a Madman" is by Denny O'Neil, Jack Sparling and Vince Colletta. The Challengers head to a secret government lab to investigate the recent killing of some scientists there. At the lab, the Challs are attacked by a "computer-wraith" made up of bundled wires, charged with electricity. The evil spirit of the wraith is able to possess Prof (both of which look pretty cool on the cover). Trying, but unable to resist, Prof and the monster contrive to kill the rest of the Challengers, 

The remaining Challs wrap themselves with copper wire, to ground the wraith's electrical charge, and throw dynamite at the monster. Prof guesses that it was one of the scientists, Dr. Fillmore, who drove the computers mad. Just as Fillmore attacks, the dynamite goes off, leaving no sign of Fillmore or the monster. Though the Challs think the crisis is over, Prof knows that the evil spirit is still inside of him.

Edited by Murray Boltinoff.