"It is there that the blow must be struck. But how?"

Yes. How? There was at the service of hatred in that delicate woman, in
appearance oblivious of worldliness, that masculine energy in decision
which is to be found in all families of truly military origin. The blood
of Colonel Chapron stirred within her and gave her the desire to act.
By dint of pondering upon those reasonings, Lydia ended by elaborating
one of those plans of a simplicity really infernal, in which she revealed
what must be called the genius of evil, for there was so much clearness
in the conception and of villainy in the execution. She assured herself
that it was unnecessary to seek any other stage than the studio for the
scene she meditated. She knew too well the fury of passion by which
Madame Steno was possessed to doubt that, as soon as she was alone with
Lincoln, she did not refuse him those kisses of which their
correspondence spoke. The snare to be laid was very simple. It required
that Alba and Lydia should be in some post of observation while the
lovers believed themselves alone, were it only for a moment. The
position of the places furnished the formidable woman with the means of
obtaining the place of espionage in all security. Situated on the second
floor, the studio occupied most of the depth of the house. The wall,
which separated it from the side of the apartments, ended in a partition
formed of colored glass, through which it was impossible to see. That
glass lighted a dark corridor adjoining the linen-room. Lydia employed
several hours of several nights in cutting with a diamond a hole, the
size of a fifty centime-piece, in one of those unpolished squares.

Her preparations had been completed several days when, notwithstanding
her absence of scruple in the satiating of her hatred, she still
hesitated to employ that mode of vengeance, so much atrocious cruelty was
there in causing a daughter to spy upon her mother. It was Alba herself