He had a strong suspicion of the letter's purport.

Ruth would have reviewed her conduct that night at Sarita Creek, and, with her instinctive cunning, perceived it would alienate Lee.

The message doubtless carried an adroit explanation and excuse, ending up with numerous declarations of her affection and hypocritical assertions of her anxiety on his account.
Disgust overwhelmed him.

He was minded to cast the thing into the stove unread.

At last, however, muttering to himself, he thrust a forefinger under the flap and ripped the envelope open.