Greenhall, K: Deathchain

From the author of Elizabeth and Childgrave comes the chilling tale of a computer generated chain letter that instructs a group of emotionally ill recipients to kill a stranger, bringing about a series of grisly murders in the town of Dale Falls, New York in this suspenseful mystery. “Dear Prospective Killer: There is someone you wish dead…”
This is no ordinary chain letter. Its rules are simple. Its results are grotesque. Its consequences look like a string of accidents, or the work of a twisted serial killer acting alone.

As recipients of the letter fall for its request, slowly and horribly, the population of Dale Falls drops, one by one by one…You kill a stranger, then a stranger will kill for you, but break the chain, and you will be killed.

In the midst of the crimes, Paul Marnay, divorced father, amateur sleuth, and a target of death, is about to learn that a deadly chain is only as strong as its most demented link—the controlling link—the Chainmaster.