Garth and Bev - Lightbulb

Animation about a time-travelling brother and sister called Garth and Bev, who live in harmony with nature in their village long ago. They are transported to different times and places by the Time Spiral and solve problems with the help of Grandfather Lir. Garth and Bev are painting pictures for the Ballybeg Storytelling, but no one will see them if they can't light Grandfather Lir's cave up, and a pesky fly muddling up their drawings isn't helping either! But when the children figure out he's a firefly and can make light in the dark, they just have to persuade him to bring all his friends! Through the Time Spiral they meet Thomas Edison, who is trying to solve a very similar problem...