He left Scotland Yard a little while after this, a much puzzled man. His first call was at the flat in Edgware Road which Odette Rider occupied. She was not at home, and the hall porter told him that she had been away since the afternoon of the previous day. Her letters were to be sent on to Hertford. He had the address, because it was his business to intercept the postman and send forward the letters. "Hillington Grove, Hertford." Tarling was worried. There was really no reason why he should be, he told himself, but he was undoubtedly worried. And he was disappointed too. He felt that, if he could have seen the girl and spoken with her for a few minutes, he could have completely disassociated her from any suspicion which might attach. In fact, that she was away from home, that she had "disappeared" from her flat on the eve of the murder, would be quite enough, as he knew, to set the official policeman nosing on her trail. "Do you know whether Miss Rider has friends at Hertford?" he asked the porter. "Oh, yes, sir," said the man nodding. "Miss Rider's mother lives there." Tarling was going, when the man detained him with a remark which switched his mind back to the murder and filled him with a momentary sense of hopeless dismay. "I'm rather glad Miss Rider didn't happen to be in last night, sir," he said. "Some of the tenants upstairs were making complaints." "Complaints about what?" asked Tarling, and the man hesitated. "I suppose you're a friend of the young lady's, aren't you?" and Tarling nodded. "Well, it only shows you," said the porter confidentially, "how people are very often blamed for something they did not do. The tenant in the next flat is a bit crotchety; he's a musician, and rather deaf. If he hadn't been deaf, he wouldn't have said that Miss Rider was the cause of his being wakened up. I suppose it was something that happened outside." "What did he hear?" asked Tarling quickly, and the porter laughed. "Well, sir, he thought he heard a shot, and a scream like a woman's. It woke him up. I should have thought he had dreamt it, but another tenant, who also lives in the basement, heard the same sound, and the rum thing was they both thought it was in Miss Rider's flat." "What time was this?" "They say about midnight, sir," said the porter; "but, of course, it couldn't have happened, because Miss Rider had not been in, and the flat was empty." Here was a disconcerting piece of news for Tarling to carry with him on his railway journey to Hertford. He was determined to see the girl and put her on her guard, and though he realised that it was not exactly his duty to put a suspected criminal upon her guard, and that his conduct was, to say the least of it, irregular, such did not trouble him very much.