He heard her turning the key in her bedroom door with a determined click.
He read her letter over again twice.

The ridiculous little phrases convinced him of the groundlessness of his suspicion.

Punctuation would have argued premeditation, and premeditation guilt.

"Nevill has come home--why of course you saw him." She had actually forgotten that Stanistreet had been there on the evening of his arrival.
He laughed so loud that Mrs.Nevill Tyson heard him in her bedroom.
An hour later he heard her softly unlocking her door.

He smiled.