S5·E30 Lost and Found

When things begin to go missing around the house like Mommys keys - Mommy blames Gilbert. Caillou is sure Gilbert didnt take them... and he sets out to prove it! Together, Caillou, Mommy and Rosie backtrack through the house and eventually discover Caillous theory was right Gilbert didnt take the keys -- Mommy left them in the door handle!