Laura and Mary get an assignment from school that involves collecting insects and observing them. Caroline makes the girls allow Carrie to go along with them.
Of course, Carrie gets into plenty of mischief and frustrates Mary, particularly when she lets the little critters loose. Mary yells at Carrie and tells her to stay put.
But Carrie is awed by a beautiful butterfly and goes chasing after the gracefully-flying monarch. The amazement ends when the ground falls out from under the 5-year-old Ingalls girl ... she's fallen into a mineshaft. Mary and Laura run home and immediately tell their Ma and Pa.
Charles immediately organizes a rescue effort to save his little daughter's life. Working late into the night, a drunkard named Mr. Laudy keeps pestering them, wanting to tell the workers something? But what?
After ignoring the ex-miner for awhile and chalking his rambling to the effects of the booze, Charles finally listens. Mr. Laudy might just know a path inside the mine that will lead to the shaft where Carrie is trapped. The group manages to find Carrie ...
... but all seems lost when Caroline hears a cave in. The sad music plays and it's tissue time ... until the real tears start flowing. Carrie is standing right in front of her, filthy dirty from the dust, but safe! Caroline hugs her youngest daughter in celebration.
Oh, and everyone else is OK, too!