When Dick hears that Duncan might be moving his new girl-friend,Sister Potts, into the flat,he fears for his tenancy. After becoming a responsible doctor at work and waiting on Duncan at home,he concocts a story that he is engaged to fearsome Sister Fletcher,and wants her to move in but offers to break it off if Duncan gives up his girl-friend. Actually Sister Fletcher is unaware that she has just got engaged but soon will be as Duncan plans his revenge on Dick.