Ruth Madoc, Prof Heinz Wolff, Deborah Leigh Hall

His Highness the Rangdo of Arg has arranged a particularly tricky set of problems for this week's explorers. How many Argonds are lurking round the pond, and how are the explorers expected to get through the Crystal Mine when the anti-gravity boots are chained up? Tackling these and other puzzles this week are Ruth Madoc, Professor Heinz Wolff and Deborah Leigh Hall