Captain Rex Larrymore, a former RFC pilot turned diamond prospector has an idea for Air Commodore Raymond and Biggles. While searching for diamonds in the island of Borneo, he had set up a private airstrip in a remote dry lake bed in the mountains. When the Japanese invaded Southeast Asia he had fled but doubted if the Japanese knew about the existence or location of the airstrip. It would be ideal as a base for a secret strike force to attack Japanese troops and rear area communications.
Biggles likes the idea and, being assured of a free hand from Raymond, soon sets up a base called Lucky Strike with three Beaufighters and a Liberator bomber manned by his 666 squadron. There, Rex introduces Biggles to Suba, the chief of the local Punan tribe, who agrees to help.
The next morning, Biggles leads his Beaufighters out on patrol and spots a small sailing boat pursued by a Japanese patrol craft which he attacks and sinks. Next they encounter a Mitsubishi A5M Claude-a carrier-borne fighter. Biggles follows and so finds an aircraft carrier in Kuching harbour with aircraft lined up neatly on deck. Biggles promptly attacks it while directing Algy to attack nearby shore installations.
Returning to Lucky Strike, Biggles learns from Suba's "bush telegraph" that a small boat is moving upriver pursued by Japanese 40 miles away. Surmising that it must be the boat they saved on their first patrol, Biggles takes off in search while Rex accompanies a group of Punans through the jungle. Biggles finds the boat under attack from a Kawanishi seaplane which he shoots down, after which Ginger parachutes down with medicines and supplies.
Ginger meets the occupants of the boat, Jackson, a British diplomat, and two American naval aviators Gray and Flannagan, escapees from a Japanese prison camp at Cotabato on the Filipino island of Mindanao. Japanese pursuers soon arrive on boats but they are beaten back by Beaufighters from Lucky Strike, after which Ginger and the others are rescued by Rex's Punan warriors and brought to Lucky Strike.
Jackson briefs Biggles about Catobato. The prison there holds the captured American General Barton, a number of Allied personnel as well as some civilians including two women. Next to the prison is an important Japanese ammunition dump. Biggles considers a rescue attempt but first sends Angus off in the Liberator to Darwin for approval while Bertie, Gray, Algy and Ginger are sent in two Beaufighters to reconnoitre and photograph Cotabato.
The reconnaissance goes well but on the return trip, Ginger and Algy discover a krait (a highly venomous snake) in their aircraft and are forced to crash land on an island where they are captured. They are taken by a Japanese submarine to Cotabato where they are interrogated by the local Japanese commander, Yashnowada and then thrown into the prison camp.
Biggles, on hearing the news, goes in search, and, not finding Algy and Ginger on the island, spots the wake of a submarine, and concludes that they must have been taken to Cotabato. Angus Mackail's group of pilots return in the Liberator, bringing news of the approval of Biggles' plan as well as a Cayman amphibian which would be needed in the rescue attempt.
The rescue goes off smoothly. The ammo dump is blown up and the prison is sprung. The rescued prisoners are soon brought back to Lucky Strike and ferried to Australia in the Liberator. But before the squadron can rest, there is an unwelcome visitor in the form of a Japanese navy reconnaissance flying boat which spots the airstrip. Thinking that the blue moss on the surface of the rock must be water, it foolishly comes in to land and promptly crashes and bursts into flames. All would have been well but then a Nakajima fighter also spots the commotion on the ground and flies away.
Next comes a British amphibian bearing Wing Commander Crane and Fee Wong, a Chinese merchant and one of the prisoners Biggles rescued from Cotabato. Fee Wong brings news that the Japanese are planning to move a valuable convoy of rubber and tin by the Limpur river across the Malayan peninsula to the east coast for shipment to Japan. The convoy of barges would pass his sawmill at Telapur and could be attacked. Biggles departs in the Cayman with Fee Wong, Algy and Ginger for the mission but on the way, they meet a strong headwind with cuts into their fuel reserve, making it impossible to return to Lucky Strike.
They proceed on the mission nonetheless. Biggles puts down on the river near Telapur and learns that the barges at moored at the sawmill under heavy guard. The convoy had halted because a pontoon bridge had been erected across the river for the movement of some Japanese troops. With the monsoon rains starting and the river flooding fast, Biggles hatches a plan of attack. Using Fee Wong's elephants, large quantities of teak logs are pushed into the river and floated downstream in swift current to act as battering rams. The attack is successful and the barges are torn from their moorings while the bridge is brought down together with a large body of Japanese troops and vehicles which was crossing the river at that time. Biggles then hijacks a Kawanishi seaplane and uses its fuel for the Cayman's return flight.
Arriving at Lucky Strike, Biggles finds the base out of action from a series of enemy bombing raids. Ginger is taxying the Liberator, their last serviceable aircraft into hiding when yet another raid is spotted. Acting instinctively, Ginger takes off, intending to save the aircraft and head to Australia for reinforcements. On the way, Ginger is intercepted by Fulmar fighters and asked to land on the Australian aircraft carrier HMAS Adelaide. After hearing Ginger's report, the captain of the carrier agrees to let Ginger lead a squadron of Fulmars back to Lucky Strike to beat off further attackers.
Ginger times his arrival at dawn and is just in time to intercept and destroy yet another raid of Japanese bombers. After a largely one-side battle, the victorious Fulmars return to the carrier while Ginger rejoins his squadron mates at Lucky Strike.. Not long after, Air Commodore Raymond arrives with reinforcements and the news that Lucky Strike would now be established as a strike base on a permanent footing with regular squadrons of fighters and bombers of the Royal Australian Air Force. Biggles and his squadron mates, having done their job, depart for Australia for a much needed rest.