The two-edged sword is a reference to hypnotism and the fact that it can produce good or bad effects. In the case of Fay Bridges who, years earlier was hypnotised by a quack doctor, it has had a lasting unfortunate effect in her relationship with her husband. Dr. Corder, however, is able to use it to the good in the case of Doreen Stokes in helping her come to terms with the baby she has rejected.