Pearls are at centre of this story, dealing both with attempts to steal them and murder.

goodreads summary

Biggles is asked to help a Chinese resident of Malaysia, called Lin Seng, move his unique pearl collection to London. Amongst this priceless collection is a superb pearl known as "the Blue Moon of Asia". Flying out to Malaysia and over Taihan, Seng's fantastic home, Biggles finds no suitable landing place. Going to Kuala Lumpur, Biggles makes contact with one of Seng's business managers called Tong. He tells Biggles that telephone contact has been lost with Taihan. Biggles and Algy hire a car and drive out to investigate. Finding a break in the telegraph lines, Biggles discovers the body of a Post Office worker sent out to repair the fault. The lines have been cut and when Biggles fetches the local police, the body has disappeared. Pressing on to Lin Seng's home at Taihan, Biggles finds he is under siege from thieves who want to steal his pearl collection. Twenty loyal workers defend Seng. Algy uses these workers to start to clear an overgrown golf course to turn it into a makeshift landing strip. The situation takes a turn for the worse when news is received that fifty Indonesian guerrillas have landed and are suspected to be making for Taihan. Biggles decides to try to break out, to get to Kuala Lumpur whilst Algy finishes the airstrip. Here he can alert the Malaysian Government to the Indonesian incursion and bring the plane to Taihan to land and collect Lin Seng and his pearls. Leaving by car with Ayart, one of Seng's servants, Biggles is brought to a halt and captured by the thieves in the jungle. Algy decides to block the entrance to the golf course by destroying a fallen tree over a crocodile infested ditch. Using gelignite, he blows the tree to pieces and this helps facilitate Biggles' escape because the thieves were taking Biggles to the golf course and they are caught in the explosion. Finishing the airstrip, Algy and Lin Seng are preparing for evacuation when the Indonesian troops attack. Biggles arrives by plane and with him come Malaysian Government soldiers. Algy saves Lin Seng from a murderous attack in an effort to steal his pearls and he is finally flown to safety. The picture on the dust cover shows Algy about to blow-up the tree bridge under a watching moon.