My Naughty Little Sister's Friends

The narrator’s naughty little sister is always doing silly things. She's curious about what's in the chimney, so she sticks a feather duster up there. When all the soot falls out, she tries to hide it! But when she has measles she's itchy and sad and grumpy and has to stay in bed—and can't be naughty at all! How long before she's bad again?