Bill Gray was a U.S. Navy pilot who appeared in Biggles in Borneo. Prior to meeting Biggles, he had been shot down by the Japanese while out on a reconnaissance flight over the Philippines. He and his gunner, Pat Flannagan had been taken prisoner and sent to the Cotabato prison camp where they had met Jackson, a British diplomat who had also been captured. Gray and Flanngan attempted to escape but had been recaptured. As they had struck a Japanese soldier during their escape attempt, General Yashnowada, the brutal commander of the prison camp, had sentenced them to be flogged. The punishment, however, only strengthened their determination to escape again and they made a second attempt together with Jackson, which succeeded.
Gray, Flannagan and Jackson stole a sailibng boat and attempted to reach Australia. However, when sailing down the coast of British North Borneo, they were discovered and pursued by a Japanese patrol boat. Fortunately the Japanese boat was spotted and sunk by Biggles and the others on their first patrol out of Lucky Strike.
Short of food and water, the trio had turned inland, proceeding upriver in their boat but Japanese troopsin canoes continued to pursue them, guided by a Kawanishi E7K seaplane. Forty miles from Lucky Strike, their plight was spotted by Punan warriors in the jungle and the news transmitted to Lucky Stirke. Ginger suggested packing a survival kit with food and medicines to be dropped to them. Biggles agreed and took Ginger up in a Beaufighter while Captain Rex Larrymore and Suba led a rescue party to try to reach them overland. The Beaufighter found Gray's boat under attack from the Kawanishi seaplane and promtply shot it down. Ginger then parachuted down with the supplies, meeting Jackson, Gray and Flannagan, who had come ashore after their boat had been sunk by the seaplane.
By the next morning, the Japanese pursuers had almost reached the Ginger and survivors but were destroyed by Suba's warriors and the Beaufighters just in time. Gray and the others were then carried to Lucky Strike by the Punans, an overland trip through the jungle taking two days.
Despite his injuries from the flogging, Gray declined to be evacuated to Australia. He told Biggles he wanted to remain at Lucky Strike to help. He had stationed at Manila and had served on an aircraft carrier cruising among the Filipino islands for a long time. He knew the coasts and waters very well.
Biggles agreed to Gray remaining. Taking advantage of his local knowledge, Biggles despatched him with Bertie to conduct a photo-reconnaissance of Cotabato. They returned to Lucky Strike with the photos and also with a report that Algy and Ginger had baled out over Talut Island.
Gray's role in Biggles' rescue mission to Cotabato was not described but it was likely he would have flown in one of the strike aircraft, either the Liberator or the two Beaufighters. By then, 666 Squadron was already shorthanded and a pilot with local knowledge of the target area like Gray would most certainly have been used.
At the end of the book, Gray departed Lucky Strike on board a Liberator together with Biggles, Jackson, Pat Flannagan and the rest for a well-earned rest in Australia.