In Biggles Foreign Legionnaire Cy Lindsay was an American ex-member of the war-mongering syndicate. He was a mechanic working in New York before becoming employed by Fabiano Pantenelli. He worked for two years as Pantenelli's personal driver and so got to know many of the top figures in the syndicate. However, after his younger brother got killed in Korea he blamed the syndicate for causing wars and making money out of them. He left the syndicate and swore to eliminate its top leaders one by one.
Before meeting Biggles in Alexandria, he killed Nestor Janescu who had just arrived there in his yacht. Later, he killed Johann Klutz at the Hotel Continentale just when Biggles and Ginger returned to the hotel from a visit to the Aladdin's Lamp night-club. Lindsay assumed Biggles and Ginger were also members of the syndicate and so tried to shoot them also but was knocked off balance when Biggles leapt at him. After a brief struggle, Biggles and Ginger disarmed him and convinced him that they were police officers. Lindsay calmed down enough to tell his story and also provided much background information on the syndicate--who its leaders were, and most crucially, the location of the syndicate's secret bomber squadron. They were surprised by Leffers, who had himself also returned to the hotel and Lindsay shot him also. Biggles told Lindsay he had more important things to do than concern himself with Lindsay, who seemed bent on suicide anyway. However, he gave Lindsay some money and asked him to go to London and report to Air Commodore Raymond. Parting ways, Lindsay did as Biggles asked and his report served to bring Air Commodore Raymond down to Egypt where he proved to be of great help to Algy, Bertie and Marcel as they attempted to follow Biggles' trail to the location of the secret squadron. After reporting to Raymond, Lindsay disappeared and was never seen again.
Lindsay's actions play an important, or even the largest, part in bringing down the war-mongering syndicate. It could even be argued that what he started would have been enough to ensure its demise. By his own analysis, by killing Klutz, he had forced the remaining committee members Pantenelli and Hugo Festwolder to come out into the open to manage the operations of the syndicate themselves. Although Lindsay didn't know it, this had the effect of causing the two leaders to fly out to the Valley of the Tartars where they were eventually killed by raiding Kurdish tribesmen.