Champagne per uno

Recruited as a chaperone at a reception for mothers-girls, Archie Goodwin assists helplessly with the death of one of the two young escorts, Lucia, poisoned with arsenic. The police are sure it is suicide, but Archie is convinced of the opposite, and initially Nero Wolfe suspects the victim's ex-boyfriend, who had been abandoned to the news of the pregnancy and later lost the child.