All that was needed was to prove that Christine had had two opportunities of tampering with the watch.
I found those easily enough.
She had been alone in Linda's room that morning - and there was an indirect proof.
Linda was heard to say that she was 'afraid she was going to be late,' but when she got down it was only twenty-five past ten by the lounge clock.
The second opportunity was easy - she could alter the watch back again as soon as Linda turned her back and went down to bathe.
Then there was the question of the ladder.
Christine had always declared she had no head for heights.
Another carefully prepared lie.
"I had my mosaic now - each piece beautifully fitted into its place.
But unfortunately I had no definite proof.
It was all in my mind.
It was then that an idea came to me.
There was an assurance - a slickness about the crime.
I had no doubt that in the future Patrick Redfern would repeat his crime.
What about the past?
It was remotely possible that this was not his first killing.
The method employed, strangulation, was in harmony with his nature - a killer for pleasure as well as for profit.
If he was already a murderer I was sure that he would have used the same means.
I asked Inspector Colgate for a list of women victims of strangulation.
The result filled me with joy.
The death of Nellie Parsons found strangled in a lonely copse might or might not be Patrick Redfern's work - it might merely have suggested choice of locality to him, but in Alice Corrigan's death I found exactly what I was looking for.
In essence the same method.
Juggling with time - a murder committed not, as is the usual way, before it is supposed to have happened, but afterwards. A body supposedly discovered at a quarter past four. A husband with an alibi up to twenty-five past four.
"What really happened?
It was said that Edward Corrigan arrived at the Pine Ridge, found his wife was not there and went out and walked up and down.
Actually of course he ran full speed to the rendezvous, Caesar's Grove (which you will remember was quite near by), killed her and returned to the cafe.
The girl hiker who reported the crime was a most respectable young lady, games mistress in a well-known girls' school.
Apparently she had no connection with Edward Corrigan.
She had to walk some way to report the death. The police surgeon only examined the body at a quarter to six.
As in this case the time of death was accepted without question.
"I made one final test. I must know definitely if Mrs Redfern was a liar.
I arranged our little excursion to Dartmoor.
If any one had a bad head for heights, they are never comfortable crossing a narrow bridge over running water.
Miss Brewster, a genuine sufferer, showed giddiness, but Christine Redfern, unconcerned, ran across without a qualm.
It was a small point, but it was a definite test.
If she had told one unnecessary lie - then all the other lies were possible.
In the meantime Colgate had got the photograph identified by the Surrey police.
I played my hand in the only way I thought likely to succeed.
Having lulled Patrick Redfern into security, I turned on him and did my utmost to make him lose his self-control.
The knowledge that he had been identified with Corrigan caused him to lose his head completely."
Hercule Poirot stroked his throat reminiscently.
"What I did," he said with importance, "was exceedingly dangerous - but I do not regret it. I succeeded!
I did not suffer in vain."
There was a moment's silence. Then Mrs Gardener gave a deep sigh.
"Why, M. Poirot," she said. "It's just been too wonderful - hearing just exactly how you got your results. It's every bit as fascinating as a lecture on criminology - in fact it is a lecture on criminology. And to think my magenta wool and that sunbathing conversation actually had something to do with it!
That really makes me too excited for words and I'm sure Mr Gardener feels the same, don't you, Odell?"
"Yes, darling," said Mr Gardener.
Hercule Poirot said: "Mr Gardener too was of assistance to me.
I wanted the opinion of a sensible man about Mrs Marshall.
I asked Mr Gardener what he thought of her."