Cover by John Romita. "On the Brink of Madness!", script by Steve Gerber, pencils by Don Heck, inks by Jim Mooney; Namor returns to his underworld realm to find it devastated in the wake of the nerve gas contamination; Fortunately, his subjects are just in a comatose state and amphibian scientists are eager to help them; Namor takes the scientists to Dr. Hydro's island base and then seeks out Dr. Walthers who has been working on a force field device that can protect Atlantis from any other nerve gas contamination; However, the costumed villain Force stands in his way. Namor drives him off and continues his search for Dr. Walthers; Cameos by the Inhumans, the Fantastic Four, and Spider-Man. A note from Roy Thomas and Steve Gerber explaining a printing error on 50,000 copies of Sub-Mariner #68.