She remembered the doped cigarettes.

She had heard of them before at clairvoyants'.

She saw it all--Madame Cassandra playing on Mildred's wounded affections, the broker on both that and her desire to be independent--and Drummond pulling the wires that all might take advantage of her woman's frailty.
That moment Constance determined on action.
First she telephoned to deForest Caswell at his office.

It was an unconventional thing to do to ask him to call, but she made some plausible pretext.

She was surprised to find that he accepted it without hesitating.