In The Trygon Factor, the Scotland Yard detective, Lieutenant Holst, is called in to investigate a series of daring robberies that have taken place in London's jewelry district. The thieves, who appear to be highly organized and well-informed, have stolen millions of dollars worth of precious gems and jewels from various stores and shops.
As Holst begins to investigate, he slowly uncovers a web of intrigue and deceit that leads him to the estate of the Trygons, a wealthy and reclusive English family who live in a vast and labyrinthine mansion on the outskirts of London. The Trygons are a strange and enigmatic group, who seem to have many secrets and hidden agendas.
Holst soon discovers that the Trygons share their home with a group of nuns, who are apparently engaged in some sort of religious mission or charitable work. But as he begins to investigate the nuns as well, he finds that they too have many secrets and connections to the robberies and other crimes that he is investigating.
As Holst delves deeper into the mystery, he begins to suspect that the Trygons and the nuns are not what they seem to be, and that they may be involved in a much larger and more sinister conspiracy than he ever imagined. As he races against time to uncover the truth, he finds himself drawn into a dangerous and deadly game of cat and mouse, with the fate of London and perhaps the entire world hanging in the balance.