Sir Ralph stood thunderstruck, but some one else acted. The black-bearded man had disappeared. From somewhere there were a couple of dull thuds like a hammer falling upon wood, and Foyle heard the whistle of bullets over his head. "I'll get even for that," he muttered between his teeth, but his headlong flight never slackened. Behind him was a clatter of pursuing feet. Fairfield, recovering himself, had raised a cry and it was taken up. "Stop thief! Hold him!" He passed the man who had been so eagerly intent on the bookshop. The man made a clutch at him, missed and fell headlong right in the path of Fairfield, now a few paces behind. The baronet tripped over his body and was thrown violently to the ground. Foyle made a mental note in favour of Detective-Sergeant Chambers, who had so adroitly intercepted the pursuit. As he came to the main road he slackened his pace to a sharp walk, and dived into an underground station. He breathed a sigh of relief as he passed down the steps to the platform. He had anticipated trouble, but pistol-shots in broad daylight, even in Grave Street, had been outside his calculations. He had recognised the peculiar report of an automatic pistol. His adversaries, whoever they might be, were obviously very much in earnest. Pistol-shooting at detectives is not a commonplace pastime even with the most reckless of criminals. Foyle decided on another and early visit to Grave Street, and promised himself grimly that the target should be some one else, if it came to shooting again. He was in danger of losing his temper. Not until he had got in the train did he open the note that was still between his fingers. He frowned as he read it. "Curse it! This comes of acting on impulse. Why couldn't I have waited! I had the whole thing in my hands." The note said simply-- "I am alive. I must see you. Follow the man who gives you this note.--R. G." Heldon Foyle had seen much of Robert Grell's writing during his search of the house in Grosvenor Gardens, and had no doubt that the note was his. His peace of mind was not increased by the reflection that had he waited and continued to shadow Fairfield he might have discovered the whereabouts of the missing diplomat. Now he had merely given notice as plainly as though he had shouted from the housetops that Fairfield was under observation. He had committed a blunder, and he did not forgive blunders easily, especially in himself. Even a bath and a change into his normal clothing did not restore his equanimity. In his office he found Green, with a strange excitement in his usually stolid face. "Hello, Mr. Green. What's wrong?" he demanded. The veteran chief detective-inspector pulled at his moustache. "I don't know, sir, yet. You've come just in time. Waverley is missing. "Waverley missing! That's nonsense. He was put on to relieve Norman in shadowing Ivan Abramovitch."