Fresh and spiffing after last week's cleaning challenges, our Rough Scientists are about to get all messy again. This week's challenge is to find a way to detect radioactive rocks and flammable gases. But that's not all. On day three they must explore a wet dark mine using the gas detector and a reliable light source. Hermione decides to make a cloud chamber using a jam jar. She hopes to see the trail of destruction caused by radioactive particles. First, though, she'll need to make some frozen carbon dioxide which involves a bit of help from Mike. But not all goes to plan... Mike and Ellen work on a safety lamp to detect flammable gases, which surprisingly needs a flame. Ellen sets off to make a beeswax candle using a local hive. Meanwhile Mike finds an ingenious way to use the candle flame as a gas detector using kitchen implements. Will two artfully put together sieves and some homemade beeswax candles really detect flammable gas? Meanwhile Jonathan sets to work on making a generator to power his rugged torch. With hundreds of coils of wire and some strong magnets, Jonathan can light a dim bulb by turning the magnets constantly. But when Jonathan tries to store energy in his torch, he runs into problems. What seemed simple becomes more and more tricky as the deadline approaches. Will Jonathan be able to get his lamp to illuminate the mine? And when they get there, what will the team find?