The marriage of Albert Bradley and Anne Polk Barrett was as close as anything comes, in these prosaic days, to a high adventure. Nancy's Uncle Thomas, a quiet, gentle old Southerner who wore tan linen suits when he came to New York, which was not often, and Bert's mother, a tiny Boston woman who had lived in a diminutive Brookline apartment since her three sons had struck out into the world for themselves, respectively assured the young persons that they were taking a grave chance