Following the laughter out of curiosity and amusement, Sarah and Tom discover Mia and Max in their nursery, surrounded by their beloved plush animals. Laughing uncontrollably, the twins appear to be amused by their own amusing reflections in the mirrored closet doors.

Mia and Max’s infectious laughter fills the house throughout the day. The twins are always coming up with new methods to amuse themselves and one another, from chasing the family cat with great joy to playing peek-a-boo behind the curtains. Their parents can’t resist joining in, letting their own giggles mix with the unadulterated happiness that their kids are displaying.

Sarah records a touching film of Mia and Max’s humorous antics as the day comes to an end. She spreads the twins’ contagious delight by showing her relatives and friends the video.

When Mia and Max wake up the following morning, they are excited for more fun and laughter, and their parents look forward to their children’s next outburst of laughter, which will no sure make their lives happier again.