Part 1: Rival construction companies compete for the bid to build an underground tunnel. The Dunlap company, one with a good safety record, and ran by a friend of Dan Garret is suddenly having unexplained accidents. Accidents involve workers not being properly decompressed, after working in the tunnel under water, and subject to high pressures. Dan goes undercover as a worker to investigate. As the Blue Beetle, Dan has a run in with Stanley and his trouble makeing team of workers.
Part 2: The Blue Beetle and another worker are trapped in the decmpression chamber where the bad guys are letting the pressure out too fast. Blue Beetle gets the pressure release under controlMeanwhile, the bad guys make plans to go one further and blow up the tunnel, flooding it with river water. Blue Beetle takes their plans, but will that stop Stanley and his gang? I don’t think so. As water gushes into the tunnel, Blue Beetle races to get the men out and to safety.