Dr. Mid-Nite and Hawkman head to a secret government facility and discover that the Diamond Men are already on the attack there. The duo have them disabled, but one creature pulls out the Gem Ray, blinding the JSA pair, who nearly fly into a high tension wire. Returning to HQ, the duo meet with the other members, who relate their escapes.....then a Diamond Man, Charles Crillon, walks in and spills the beans on the Diamond People, while Flash discovers that sound vibrations can destroy them. A battle ensues, the Diamond People destroyed and Crillon returned to normal.; Several mysterious events in Civic City spur the JSA to meet with Army officials, and are mystified by the uncanny predictions of a scientist named Crillon. They attend a meeting where Crillon is speaking about a race of Diamond People who live beneath the surface of the Earth whom he believes are responsible for the events happening re the Bottomless Lake and Old Reliable Geyser, and that a major catastrophe may occur if people do not act soon. When Crillon and a Mr. Exnam suddenly disappear at the meeting and the JSA reads the scientist's notebook, they decide to act.; Flash, Wonder Woman and Black Canary head to the old World's Fair grounds, where Crillon's notes indicate the Diamond People will strike. When a volcano suddenly emerges on a playground, the trio stops the lava flow and faces the Diamond People, who use a gem ray on the JSA, blinding them and plunging them into the smoking volcano. Meanwhile, at Bottomless Lake, G.L. and the Atom investigate why the lake suddenly has filled with ice. They succeed in saving the city, but the Diamond People arrive and over-power the duo with the gem ray, blinding them and causing them to go over a ciff.