Mrs. Dempster is the kindly, slightly crazy lady who lives next door to Dunny (Dunstable Ramsey, the main character).  Her husband is the Reverend Amasa Dempster.  Dunny, who is a child, is out playing one night with another boy Percy-Boyd Staunton.  While they are coming home, Percy-Boyd throws a snowball (containing a stone- - but this is not revealed until years later) at Dunny as he nears his house.  The Reverend and Mrs. Dempster are out for an evening walk (she is pregnant and needs gentle exercise) at the same moment, and the snow-rock hits her on the head, causing severe head trauma, the premature birth of her son, and permanent mental instability.

Dr. McCausland is the local country doctor, who is not very helpful with any of these problems.  Paul Dempster is the child born that fateful night, to the Reverend and Mrs. Dempster.  Mrs. Ramsey is Dunstable (Dunny's) mother,and the person who takes care of Mrs. Dempster after her trauma.