A Federation survey ship, the S.S. Ariel is crewed by a six-member scientific contact team. Leading them is Lieutenant Commander Tom Markel. Lt. Randi Bryce is a biologist, while Lt. Nancy Randolph is the ship's navigator. In 2269, the Ariel is exploring the planet Lactra VII. When the original landing party of three fails to return from its mission, Markel, Bryce and Randolph abandon their ship and beam down to find the others. Randolph gets an infection from a bug bite, and all three are soon captured by the highly intelligent Lactrans, who put them into their intergalactic zoo as exhibits. Nearly six weeks later, the three Ariel survivors are released into the care of the U.S.S. Enterprise.