Trixie reports to Speed on the radio that the tremors were probably man-made. Speed dons a diving suit which Gaynor was able to salvage. As soon as he leaves the dome he's attacked by a giant octopus. He pushes a button on his suit which releases a jet of air. The octopus takes off.
Speed gets into the dome containing the Mach Five.
Later, Dr. Seacort's rather suspicious behavior comes back to haunt him. Wexler thinks that because Dr. Seacort has openly stated that he thinks Deep Twelve is damaging the ocean's environment that Dr. Seacort might be trying to sabotage the project. Gaynor is assigned the job of keeping an eye on the doctor. Speed is out exploring in the Mach Five. He discovers a cave that looks like it was bored by machinery.