The little man with the mustaches woke up and paid for the bottle of mineral water and the thin captain's biscuits, which was all he had had.

Mitchell left the other passenger as long as possible. About five minutes before they reached Croydon, he stood by her side and leaned over her.

"Pardon, madam; your bill."

He laid a deferential hand on her shoulder. She did not wake. He increased the pressure, shaking her gently, but the only result was an unexpected slumping of the body down in the seat. Mitchell bent over her; then straightened up with a white face.

Albert Davis, second steward, said:

"Coo! You don't mean it."

"I tell you it's true."

Mitchell was white and shaking.

"You sure, Henry?"

"Dead sure. At least - well, I suppose it might be a fit." " We'll be at Croydon in a few minutes."

"If she's just taken bad -"

They remained a minute or two undecided; then arranged their course of action. Mitchell returned to the rear car. He went from table to table, bending his head and murmuring confidentially:

"Excuse me, sir; you don't happen to be a doctor?"

Norman Gale said, "I'm a dentist. But if there's anything I can do -" He half rose from his seat.

"I'm a doctor," said Doctor Bryant. "What's the matter?"

"There's a lady at the end there - I don't like the look of her."

Bryant rose to his feet and accompanied the steward. Unnoticed, the little man with the mustaches followed them.

Doctor Bryant bent over the huddled figure in Seat No. 2 - the figure of a stoutish middle-aged woman dressed in heavy black.

The doctor's examination was brief.

He said: "She's dead."

Mitchell said: "What do you think it was? Kind of fit?"

"That I can't possibly say without a detailed examination. When did you last see her - alive, I mean?"

Mitchell reflected.

"She was all right when I brought her coffee along."

"When was that?"

"Well, it might have been three-quarters of an hour ago - about that. Then, when I brought the bill along, I thought she was asleep."

Bryant said: "She's been dead at least half an hour."

Their consultation was beginning to cause interest; heads were craned round, looking at them. Necks were stretched to listen.

"I suppose it might have been a kind of fit like?" suggested Mitchell hopefully.

He clung to the theory of a fit. His wife's sister had fits. He felt that fits were homely things that any man might understand.

Doctor Bryant had no intention of committing himself. He merely shook his head with a puzzled expression.

A voice spoke at his elbow - the voice of the muffled-up man with the mustaches.

"There is," he said, "a mark on her neck."

He spoke apologetically, with a due sense of speaking to superior knowledge.

"True," said Doctor Bryant.

The woman's head lolled over sideways. There was a minute puncture mark on the side of her throat, with a circle of red round it.