It's nighttime and there's a rather loud thunderstorm. Rosie is scared, but Caillou helps to comfort her. The next morning, Mommy drives Caillou to the playschool, but finds a tree blocking the route they normally take. This old oak tree is a familiar landmark, but got blown down by the storm. Caillou's going to miss the tree and so will Mommy. She tells him, however, that a new one will be planted and reminds him that trees are special and it's important to take care of them. For the time being, they take a detour to get to the school. At school, Ms. Martin has the kids help to clean up the mess on the playground from the storm. Caillou, Leo and Clementine then decide to create a road in the sandbox heading over to the swings. The road even crosses some of the puddles made by the storm. Caillou imagines that they're driving bulldozers. They even make a bridge. Just then, Clementine puts a small sapling in the way, saying it's a big old tree. Leo says that Caillou should knock it over, but Caillou remembers what his Mommy said about trees. So he has them make a detour instead.
"Caillou's Building Adventure"
In the kitchen, Caillou's parents and his Grandpa are making jam sandwiches. They're going to be helping a family to build their new home. Caillou wants to come along and help, but Daddy and Grandpa aren't sure. Mommy suggests that maybe he just make a quick visit. She'll drop Rosie off at Grandma's and then drop Caillou off at the construction site. Once there, Daddy reminds Caillou that it can be dangerous, so he'll need to be careful. He introduces him to Sam --- the father of the family that'll be living there. Caillou imagines being a home builder and putting a home together in a flash. He then meets Sam's son, Franky. They leave handprints in the concrete.
"A House in the Sky"
Caillou is out playing in the backyard and finds an anthill. He tries to show the ants to Rosie, but she's scared and runs away. Caillou, however, imagines that he's very small and riding on the back of an ant. Just then, Mommy takes a phone call, which turns out to be from an old friend --- Carol from high school. Caillou talks to Daddy about the ones and Daddy says that while some ants can bite, the ones in their backyard are safe. Rosie lets one of them crawl up her arm --- it tickles. Mommy decides to visit Carol and it seems she has a four-year-old son named Kevin. It's a long car rid eto Carol's, resulting in several "are we there yets" from Caillou. They eventually make it, though. Kevin and Carol live in a skyscraper and Caillou has never been up that high before. He meets Kevin and asks if they can play in his backyard, but Kevin doesn't have one. So they play inside and make a skyscraper out of blocks. It comes time to leave and Caillou asks if Kevin can come to visit sometimes. Mommy agrees and Caillou suggests to Kevin that he pack a lot of books, because it's a long trip.