Kurt Swendler (Denis Goacher) and Mark Bannerman (Gerald Flood) are clearing rocks from the backup oxygen system when the valve on Kurt’s air tank fails.  Mark saves Kurt’s life.  Ann (Caroline Blakiston) and Peter (Stewart Guidotti), aware that one of them has a faulty tank, go out to try to help.  Peter slips and gets caught in the vicious current that surrounds Aegiria and is swept away.  Mark dives into the current after him.  Mark manages to find Peter and get him back to Aegiria.    

Everyone thinks both men are dead until they come through the airlock.  Swendler finds out that Mark sabotaged the oxygen extractor but because Mark saved his life, he keeps the information secret.  He tells Ziebrecken (Aubrey Morris) that one of the bearings had a flaw and suffered stress fatigue. 

Ziebrecken convinces Professor Westfield (Hayden Jones) that what he is doing is for the benefit of all mankind and not for any one government.  He decides to assign Peter to work with the Professor.  Peter is not so sure of Ziebrecken’s noble claims.

Ziebrecken tells Swendler that he needs to go to, what Ziebrecken refers to as, the cellar and get the luggage.  The statement makes Swendler extremely uncomfortable.  He tells Swendler to take Mark with him so he can write an article about it.  The cellar is an underwater room over 35,000 feet down.  To get there they need to take the Bathyscaphe.  Once they descend and are in the cellar, Mark sees a bunch of cylindrical containers.  Swendler is secretive about them but Mark refuses to help until he knows what they are.  Swendler confesses that they are nuclear missile warheads.

A bathyscaphe was a deep diving vessel that was designed by Swiss scientist Auguste Piccard.  It was designed to reach extremely deep ocean depths.  The deepest recorded depth of a bathyscaphe is about 35,797 feet.  It was done by the Trieste, a Swiss bathyscaphe that descended into the Challenger Deep of the Mariana Trench in 1960.  The Trieste was designed by Auguste’s son Jacques Piccard and US Navy Lt. Don Walsh.