Things that go bump in the night, and others that light up the sky, are on everyone's mind today. A family corn roast dinner at Grandma and Grandpa's under the star-studded sky prompts Grandpa to bring out his telescope and introduce Caillou to the constellations, planets, and moon. Grandpa discovers a new planetarium is opening and there's a prize for the best space costume. Caillou is thrilled when the winner turns out to be...a surprise! But fun turns to fear at bedtime when Caillou decides that a monster is lurking in his room. All's well when Mom and Dad unmask Caillou's monster as a tree branch on the window! Then, during a winter storm, the lights go out and Caillou is very afraid. Dad builds a fire in the fireplace and the family pretends they're camping. They even toast marshmallows!