Mandy and James are on holiday with Mr and Mrs Hope as they visit an old friend who works on a lodge in South Africa. While they are there, they meet resident big cat expert, Sandie Howard,, who tells them about Leela, a leopard cub who was found abandoned some years back and who has been raised on the site. Leela has a tracking device and has recently had cubs of her own. But when the tracking device goes out of range, Sandie is concerned - she never usually wanders far. When they eventually find Leela it looks like she's been drugged, and her cubs taken. Sandie says there are smugglers who steal leopard cubs for unscrupulous private collectors and she thinks this is what might have happened. Mandy discovers evidence incriminating some mystery visitors to the area and eventually they track down the cubs and return them to their mother.