A serial killer is on the loose in San Diego, and he has a most unusual M.O.: With each kill, he leaves behind objects with unclear meanings. Most of the recent killings are centered near Kendra Michaels' home and office, so it comes as no great surprise when the FBI shows up at her door. The investigators soon make a startling discovery: the left-behind objects are actually souvenirs of other unsolved serial murder cases in various U.S. cities. The investigators become his newest targets, even as Kendra slowly begins to suspect that one of them may be the killer himself.