In "The Scarlet Letter", who does Hester recognize in the crowd and what vow does she make?

Hester recognizes her husband, Roger Chillingworth, who has returned from the Indian settlement for ransom. He recognizes her, but she signals him to be quiet.

Through his conversation with a townsman, Chillingworth learns the father of Hester's baby is unknown; despite the pleading of man of the powerful men in town, Hester refuses to talk. Chillingworth then vows that he will find out the identity of the man that is the father of the child and helped cause Hester to be outcast.