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.