Originally aired: September 21, 1969 on ABC
Writer: William L. Stuart
Director: Harry Harris
Show Stars: Don Marshall (Dan Erickson), Deanna Lund (Valerie Ames Scott), Heather Young (I) (Betty Hamilton), Gary Conway (Captain Steve Burton), Stefan Arngrim (Barry Lockridge), Don Matheson (Mark Wilson), Kurt Kasznar (Commander Alexander B. Fitzhugh)
Recurring Role: Erik Nelson (S.I.D. Officer)
Guest Stars: William Chapman (Secretary Mek) , James Daris (Super Giant Robot) , Broderick Crawford (Professor Gorn) , Stuart Margolin (Zoral) , Steven Marlo (Minor S.I.D. Official) , Richard Carlyle (Special Policeman)
Production Code: 4703
Mark and Fitzhugh are captured by a giant after witnessing a bulletproof man kill a policeman during a break-in. The giant, Professor Gorn, is a scientist who was monitoring his creation: a robot. They want Mark to lend his technical expertise to iron out the little bugs like the fact it kills people. Gorn and his assistant Zoral use Fitzhugh as a test experiment to prove Mark's theory that the robot has the equivalent of a defective adrenal gland.
Meanwhile, Steve, Dan, and Valerie break in using their laser drill. Mark eventually irons out the bugs. Steve and Dan help Mark escape, and all three take refuge in the robot. Fitzhugh deliberately gives away Valerie's presence, then spins a tale about how the Earthlings are master saboteurs. That gives Mark time to rig the robot so he can run it by remote control.
When Gorn calls in a Council member to witness his triumph, Mark has it free Fitzhugh and Valerie, then attack its creator and destroy the lab. Gorn is killed, although Zoral escapes.