Three young cousins (ages 7, 8 and 9) spend their annual week with Grandma and Grandpa in Minnesota. In addition to the normal fun activities planned by their grandparents, they initiate an adventure all on their own.
When they take a secret hike to a local cave, they are surprised by other people coming and hide. They hear some older boys bury a box. What is it, they can't wait to see. And this starts their adventure; one they can't tell grandma and grandpa about because they never should have been in the cave in the first place.
Unknowingly, they have also discovered an important Indian artifact.