Penny the mouse is out for a walk when she spots something shiny and beautiful in her neighbor's yard. Resting perfectly in Mrs. Goodwin's green grass is a bright blue marble. Penny loves it instantly and decides to slip it into her pocket and take it home. But as soon as she gets back to her room, the beautiful marble does not feel quite as wonderful anymore. Penny's stomach starts to tie in knots, and she cannot stop wondering if the marble actually belongs to Mrs. Goodwin. Her guilt grows bigger and bigger, making it impossible to enjoy her new treasure. Finally, Penny realizes there is only one way to make the heavy feeling go away. She must be brave, march back to her neighbor's house, and return the marble. Join Penny on a gentle journey about honesty, doing the right thing, and the relief of telling the truth.