What mysterious events drive the plot in the novel, The Waterworks?

The mystery involves the disappearance of a free lance writer after he tells of seeing his supposedly dead and buried father being driven up Broadway with several old men dressed in black. Detective work then reveals the corpse of a child in the father's grave, a family that did not receive the fortune of the "deceased," and a new orphanage in the city with children who have an unexpected reason to be frightened. The orphans are being used in medical experiments to prolong the lives of vain old men who have secretly given their money to a strange doctor in the hopes of outwitting death.