Liz Bonnin takes us inside the dramatic world of big animal surgery. This time, she travels to a sanctuary in Sierra Leone to witness a lifesaving operation on a young chimpanzee. The chimp has a rapidly growing lump on her abdomen, which her keepers are worried is a cancerous tumour. One of the world’s leading wildlife vets uses advanced techniques from human medicine to diagnose and remove the lump. But the story takes a dangerous twist when the chimp nearly wakes during the operation.