After finding a photograph of a four-year-old Dad with a model train set, Caillou and Dad decide to look for it in Grandpa’s basement. After a while, they finally find it and set it up to test it out. Caillou is having a great time; Grandpa, Dad and Caillou all love toy trains. Grandma captures the moment in a photograph which Caillou decides to put in the photo album beside the old picture of Dad.