Hardt grinned. “An organization like ours has friends everywhere. When Muller approached the firm of publishers you’re supposed to be representing, the directors had a word with Sir George Harvey, one of their biggest shareholders. He got in touch with the Foreign Secretary, who put the matter in the hands of the Bureau.”

Chavasse frowned. “What do you know about the Bureau?”

“I know it’s a special organization formed to handle the dirtier and more complicated jobs,” Hardt said. “The sort of things MI5 and the Secret Service don’t want to touch.”

“But how did you know I was traveling on this train to meet Muller?” Chavasse said.

“Remember that the arrangement with Muller, by which he was supposed to contact you at Osnabruck, was made through the managing director of the publishing firm. He was naturally supposed to keep the details to himself.”

“Presumably, he didn’t.”

Hardt nodded. “I suppose it was too good a tale to keep from his fellow directors and he told them everything over dinner that same evening. Luckily, one of them happens to be sympathetic to our work and thought we might be interested. He got in touch with our man in London, who passed the information over to me at once. As I was in Hamburg, it was rather short notice, but I managed to get a mid-morning flight to Rotterdam and joined the train there.”

“That still doesn’t explain how the people who killed Muller knew we were supposed to meet on this train,” Chavasse said. “I can’t see how there could possibly have been another leak from the London end. I don’t think it’s very probable that there’s also a Nazi sympathizer on the board of directors of the firm I’m supposed to be representing.”

Hardt shook his head. “As a matter of fact, I’ve got a theory about that. Muller was living in Bremen with a woman called Lilli Pahl. She was pulled out of the Elbe this morning, apparently a suicide case.”