How can a mischievous schoolgirl save the world? Nel is full of ideas, and when she realises that there is a fiendish plan in the offing, she sets out on an adventure to find the beast that is determined to destroy the planet. With colour illustrations by John Lund, this story is full of advice and ideas about how children can look after their planet.

Sut all merch ysgol ddireidus fel Nel achub y byd? Mae Nel yn llawn syniadau fel arfer, a phan mae'n deall bod yna gynllun dieflig ar droed, mae'n mynd ar antur i ddod o hyd i'r bwystfil sy'n benderfynol o ddinistrio'r blaned. Yn ogystal â stori, a lluniau lliw gan yr artist John Lund, mae'r llyfr yn llawn cyngor a syniadau am sut y gall plant wneud eu gorau i ofalu am y blaned.