Originally aired: Sunday January 11, 1970 on ABC
Writer: Richard Shapiro
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)
Guest Stars: Jonathan Harris (The Piper) , Peter Leeds (Senator) , Michael-James Wixted (Timmy)
Production Code: 4718
Dan, Fitzhugh, and the women are lured into a cage by hypnotic pipe playing. The piper reveals himself as a rather fey-looking alien being, a giant on this planet, who is apparently the Pied Piper of Hamlin. He tries to sell the Earthlings to a senator for a reward, while the other Earthlings secretly follow.
The senator refuses, so the Piper tries to take his child. Dan thwarts the attempt by having the senator record the Piper's music, loop it, and play it backwards (good one, Dan!). The senator still refuses to free them, so Mark and Steve trip the senator and free the rest. The Piper, reverting to human/Earth size, then confronts the Earthlings and offers them a deal: help them get the senator's child and he'll take them home. The group righteously refuses, except for Fitzhugh, who secretly contacts the Piper.
With the aid of an unwitting Barry, Fitzhugh turns off the protective tape and the Piper gets the boy and takes him to his extra-dimensional home. Steve and the others find out and force Fitzhugh to take them there as well, where they plan to use Fitzhugh's money to buy the kid. The Piper will honor his deal to take them home...in 700 years when he is in the vicinity! Fitzhugh angers him and the Piper challenges him to a version of the classic shell game...with first Chipper, then Betty, then Barry as the "pea".
Fitzhugh refuses to play, and Steve screws up spotting the "pea" the first two times. With Barry on the line, Fitzhugh plays and manages to spot him thanks to some judicious cheating. An irritated Piper attacks the group, but Steve has put red peppers in his horn. They use the distraction to escape once and for all.