The mysterious woman had actually been in the smoking-room with him.
If Lady Loudwater's statement that she heard her husband snoring at five minutes to twelve were to be accepted, neither Colonel Grey, Hutchings, nor the mysterious woman could have committed the murder--unless always one of them had returned later and committed it.

That possibility must be borne in mind.
But Mr.Flexen did not accept her statement.

If he were to accept it, she herself at once became the most likely person to have committed the crime.

It was always possible that she had.

She certainly had the best reasons of any one, as far as he knew, for committing it.
The evidence of Mr.Manley about the time at which he heard Lord Loudwater snore was of the first importance.