Vultureman builds a state-of-the-art infiltration robot known as the Wolfrat. He presents the robot to Mumm-Ra and assures him that this creation is capable of penetrating the Cats Lair'severy defense. Mumm-Ra, while initially dismissive at Vultureman's new creation, changes his mind after seeing a demonstration of the Wolfrat's abilities. He provides Vulturman with a vial of Miniaturization gas with which to arm the Wolfrat.
The Wolfrat then stealthily makes its way towards the Cats Lair. It avoids detection from both the lair's scan vision as well as the Sword of Omens' sight beyond sight by first transforming into a rock and then a section of the wall. It manages to drill its way into the lair and injects the Miniaturization gas into the ventilation shaft of the lair.
The gas reaches the ThunderCats and shrinks them all down to a mere fraction of their normal height. The Wolfrat takes this opportunity to attack the diminutive Cats with its laser beams. The ThunderCats are able to distract the robot just long enough for Tygra to reach his laboratory where he begins work on an antidote. At the same time, Lion-O makes his way to the Sword Chamber. Using the sword's sight beyond sight, Lion-O sees that the Mutants are already circling the lair in their flying vehicles.
Meanwhile Snarf, who had been out picking Candy fruit, arrives back at the lair only to be greeted by the Wolfrat's laser beams. Snarf pelts the robot with Candy fruit and runs away to join his fellow Cats. Panthro builds a suit of armor for Snarf and together the Cats attack and destroy the Wolfrat.
By now the Mutants have already entered the lair and are seeking to destroy the minute ThunderCats. Tygra finally succeeds in preparing the antidote and grows back to full size. He summons the other ThunderCats into his lab and they all return back to normal size. However, Snarf, who accidentally gets a whif of the antidote, grow to double his size and he alone is enough to handle the Mutants who flee for their lives.