一个平静的夏天，姆明谷爆发了大危机，火山迸发，洪水袭来。水升得越来越高，但在最后关头，姆明一家发现了一栋陌生的房子，结果这不是一个普通的房子，而是一个剧院舞台。 姆明仲夏夜狂想曲于2008年伦敦的儿童电影节上放映，深受观众们的喜爱。这一部剧场动画是取于德国和波兰制作的粘布版电视动画的16至17集内容重新制作，不同于日本的2D动画版本，粘布版系列的姆明动画拥有芬兰童话的独特风格。

One day Moomintroll wakes to notice that grey dust is covering everything in the Moominvalley. He runs to ask the philosophical Muskrat if he knows what is happening, who advises him that things tend to look like this before an awful fate coming from the sky hits the Earth. With the help of his father, Moominpappa, Moomintroll and his close friends Sniff and Snufkin build a raft and head out on a challenging journey to the observatory in the Lonely Mountains hoping to find out more from the wise professors there. The friends have to overcome several adversities in order to make it there. When they arrive, they find the professors deep in calculations. They reveal that a comet will reach the Earth in four days, four hours, four minutes and 44 seconds.