When Dipper and Mabel discover evidence that the reported town founder is a hoax, they set out to expose the historical cover-up and prove that Mabel's silliness is not a bad thing.

While Stan, Dipper, Mabel and Soos are falling in a bottomless pit, they tell stories to pass the time.

When Mabel befriends a cute merman trapped in the public pool, she's determined to help him out. Meanwhile, Dipper decides to volunteer as a lifeguard to see Wendy.

When Waddles is snatched by a prehistoric beast, Dipper, Mabel, Stan, Soos, and Old Man McGucket must journey to a mysterious land trapped in time to rescue him.