Originally aired: October 12, 1969 on ABC
Writer: Arthur Weiss
Director: Nathan Juran
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)
Guest Stars: Alex Dreier (Kronig) , John Zaremba (Dr. Lalor) , Charlie Briggs (Guard) , Steven Marlo (Technician)
Production Code: 4709
First Fitzhugh, Barry, and Valerie, then Mark, Steve, and Dan, are captured by Kronig, a giant industrialist who is a chess fanatic. He wants to demonstrate his superior mind against Earthlings. To do so, he tells them to pick their best chess player and play him. If they win, they get their freedom. If he wins or they refuse to play, he turns them over to the SID.
Barry turns out to be the best player, much to Kronig's distaste. He insists the others be tied to the major chess pieces because of the perceived insult. As an "optional" feature, the board has random trapdoors that drop the pieces into a furnace. Barry is forced to sacrifice Steve, Dan, and Mark's "pieces" to get them off the board so they can make a run for it. Mark gets back to the ship and programs the computer to play chess, helping Barry. Dan and Steve try to rig an escape.
Kronig finds out about the computer and tosses Valerie, Barry, and Fitzhugh into the furnace chamber, just as the others short out the controls and temporarily shut it down. Dan and Steve get tossed into the furnace and well, and use the laser-drill to cut their way out just before Kronig reengages the controls. Kronig and his doctor struggle and Kronig is killed when he stumbles into a panel, as the others make their escape.