The Rainy Day Killer by Michael J. McCann
A man in a business suit offers his umbrella to an unsuspecting woman … and days later she turns up dead. The terrifying Rainy Day Killer is now hunting new victims … whenever it rains. Homicide Lt. Hank Donaghue and Detective Karen Stainer team up with an FBI profiler to pursue this elusive serial predator who leaves no physical evidence behind. However, Stainer is distracted by preparations for her upcoming wedding. Uncertain about her future, she’s furious to learn that the Rainy Day Killer is threatening to make her his next victim!