Harry George Alexander Bircham, an amoral man cast from a Wildean mold, and used to getting his way, will do anything to keep the affections and attentions of Charles Holland, a fellow student at Oxford-even commit murder. I Knew Him by Erastes is the story of their summer 'vac' from Oxford, where Bircham and Holland, originally intending to visit Paris, instead return to Holland's ancestral home in Somerset. When they arrive, Holland receives a rude shock: his mother Margaret, widowed by the Great War, is about to marry the older brother of her presumed deceased husband. Holland detests his uncle, and opposes the match. Bircham eventually learns that Holland has also been visited by his father, who has been missing for several years; Holland vacillates between overwhelming rage and depression. Initially aloof to this family drama, but eventually motivated by jealousy and desire-especially the desire to protect his lover-Bircham begins causing "accidents" to occur.