The team meets Professor Sarwa, a human, who explains how Doom threatens them and their sand people. Then the team meet the delightful little critters, and Allura is particularly fond of one she calls Sandy - even giving the creature her bracelet. But then the Doom tanks roll and fun time is over. The VF launch to address the threat, but the Lions get buried in the sand. While they are incapacitated, Haggar manages to turn their friend Sandy into a Robeast. The Lions burrow deep into the sand and destroy the underground Robeast factory, but when they surface they still have to deal with the super-sized Sandy.
They realize it's their friend upon spotting the bracelet Princess gave him and do not want to destroy him...so they are in quite a pickle. That is until they surmise the big S on Sandy's chest is the source of power Haggar used to fuel the beasty Sandy and if they can remove it, he'll be okay.
Voltron is formed and just as they thought, Sandy returned to normal as soon as Voltron removed the S on his chest. Clearly defeated, the Doomies leave but not before it appears like Sandy didn't make it afterall.