The
lodgers at the Masaki home are earning their keep by helping out with
chores around the family shrine, with the exception of Ryoko, who is
being characteristically lazy. They are taking a short break when Ryo-ohki
comes running out of a cave near the shrine. Sasami asks Katsuhito about
the cave, and he tells them of the legend of a goblin that sleeps there.
He tells them that
700 years ago, a goblin came from the sky, so the people at the time
built the Masaki shrine around the cave where it became trapped to seal
in the evil monster forever. The girls are impressed by the story, and
Ryoko sees it as the perfect excuse to explore the cave. The others
turn down her offer to go exploring, but Ryoko makes other plans, and
instead grabs the reluctant Tenchi while he is walking home from school
and drags him in the cave with her.
A
short while later, Ryo-ohki finds Tenchi's abandoned schoolbag and takes
it back to the house. Ayeka realises that Tenchi must be in trouble,
and that Ryoko is missing too. She jumps to the obvious conclusion and,
with aid of a little carrot bribery, persuades Ryo-ohki to track Tenchi
down by scent and lead her to him. They follow Ryo-ohki to the cave
entrance and, led on by the ever-determined Ayeka, make their own way
through the cave.
Deeper inside the
cave, Tenchi and Ryoko encounter a series of intricate booby traps designed
to annoy and humiliate intruders. However, Ryoko easily breaks through
the traps, and the two of them soon reach a chamber at the end of the
tunnel. In the centre of the chamber is a huge crystal. 
On
closer inspection, Tenchi can see that there is something alive inside
it. While he is occupied with the crystal, Ryoko is concocting another
mischievous plan, blocking off the entrance with a rock to enjoy some
time alone with Tenchi! However, her scheme is brought to an abrupt
end when Ayeka, Sasami and Mihoshi burst into the cavern. Ayeka is shocked
to see Tenchi in such a compromising position with Ryoko, and it is
not long before a fight breaks out. Ryoko and Ayeka's battle becomes
increasingly vicious until Ryoko decides to show off her strength by
pulling the massive crystal out of the ground and hurling it at the
princess. The crystal misses Ayeka and cracks open, revealing a suspended
animation pod inside. The gang decide not to stick around to face the
legendary goblin, and beat a hasty retreat, chased by a glowing ball
of light that contains the supposed monster.
As
they reach the cave entrance, the glowing ball sets down and vanishes,
revealing the "goblin" to be a short, red-haired girl. She
introduces herself as Washu, and proclaims to be the greatest scientist
in the universe (an opinion backed up by a pair of mechanical Washu
dolls that appear on her shoulders). Washu was exiled 700 years previously
and fell to Earth inside the crystalline meteor, which was later sealed
inside the cave. Washu asks the group who it was that swung her around
inside the crystal, and when the gang points to Ryoko, she transforms
the baffled space pirate into a cute kappa* as punishment, much
to the amusement of Sasami and Mihoshi. Ayeka berates Washu for doing
something so silly, and ends up getting turned into a kappa as well!
The next day, with
Ryoko and Ayeka returned to normal, they are startled to find that Washu
has moved into the closet under the stairs in the Masaki home, and she
is busy turning it into a laboratory; the mad scientist is back in action!
