A lady and gentleman are making love to one another in the drawing room of a flat in Ashley Gardens in the Victoria district of London. The lady is a young widow, Grace Tranfield, in love with the man, Leonard Charteris, who is the 'philanderer' of the title. Grace is shocked and disconcerted to find that Charteris, on his own light¿hearted admission, has been in a similar position with Julia Craven and others. The affair with Julia, in fact, has never been broken off. He maintains that it is not his fault that half the women he speaks to fall in love with him; and he is in full flight of cajolery when Julia Craven herself erupts on to the scene, attacks Grace, and announces her intention of staying until Charteris has given her up.