“Besides,” went on Redfern confidently. “It would be absurd. Arlena was twice as strong physically as Christine. I doubt if Christine could strangle a kitten—certainly not a strong wiry creature like Arlena. And then Christine could never have got down that ladder to the beach. She has no head for that sort of thing. And—oh, the whole thing is fantastic!”

Colonel Weston scratched his ear tentatively.

“Well,” he said. “Put like that it doesn’t seem likely. I grant you that. But motive’s the first thing we’ve got to look for.” He added: “Motive and opportunity.”

IV

When Redfern had left the room, the Chief Constable observed with a slight smile:

“Didn’t think it necessary to tell the fellow his wife had got an alibi. Wanted to hear what he’d have to say to the idea. Shook him up a bit, didn’t it?”

Hercule Poirot murmured:

“The arguments he advanced were quite as strong as any alibi.”

“Yes. Oh! she didn’t do it! She couldn’t have done it—physically impossible as you said. Marshall could have done it—but apparently he didn’t.”

Inspector Colgate coughed. He said:

“Excuse me, sir, I’ve been thinking about that alibi. It’s possible, you know, if he’d thought this thing out, that those letters were got ready beforehand.”

Weston said:

“That’s a good idea. We must look into—”

He broke off as Christine Redfern entered the room.

She was, as always, calm and a little precise in manner. She was wearing a white tennis frock and a pale blue pullover. It accentuated her fair, rather anaemic prettiness. Yet, Hercule Poirot thought to himself, it was neither a silly face nor a weak one. It had plenty of resolution, courage and good sense. He nodded appreciatively.

Colonel Weston thought:

“Nice little woman. Bit wishy-washy, perhaps. A lot too good for that philandering young ass of a husband of hers. Oh well, the boy’s young. Women usually make a fool of you once!”

He said:

“Sit down, Mrs. Redfern. We’ve got to go through a certain amount of routine, you see. Asking everybody for an account of their movements this morning. Just for our records.”

Christine Redfern nodded.

She said in her quiet precise voice.

“Oh yes, I quite understand. Where do you want me to begin?”

Hercule Poirot said:

“As early as possible, Madame. What did you do when you first got up this morning?”

Christine said:

“Let me see. On my way down to breakfast I went into Linda Marshall’s room and fixed up with her to go to Gull Cove this morning. We agreed to meet in the lounge at half past ten.”

Poirot asked:

“You did not bathe before breakfast, Madame?”

“No. I very seldom do.” She smiled. “I like the sea well warmed before I get into it. I’m rather a chilly person.”

“But your husband bathes then?”

“Oh, yes. Nearly always.”

“And Mrs. Marshall, she also?”

A change came over Christine’s voice. It became cold and almost acrid.

She said:

“Oh no, Mrs. Marshall was the sort of person who never made an appearance before the middle of the morning.”