Dead Connection by Alafair Burke
When two young women are murdered on the streets of New York, exactly one year apart, Detective Ellie Hatcher is called up for a special assignment on the homicide task force. The killer has left behind a clue connecting the two cases to First Date, a popular online dating service, and Flann McIlroy, an eccentric, publicity-seeking homicide detective, is convinced that only Ellie can help him pursue his terrifying theory: someone is using the lure of the Internet and the promise of love to launch a killing spree against the women of New York City.
When the First Date killer begins to mimic a serial killer from Ellie\'s own haunted past, Ellie knows the game has become personal. Both hunter and prey, she must find the killer before he claims his next victim -- who could very well be her.
"Burke ... is a terrific web spinner. She knows when and how to drop clues to keep readers at her mercy." -- Entertainment Weekly (a "Must List" pick)
".. intricately-plotted, fast-paced ... Holds the reader's attention from first word to last, and begs for a sequel." -- Kirkus Reviews
A former deputy district attorney in Portland, Oregon, Alafair Burke is a professor at Hofstra Law School, where she teaches criminal law and procedure. The daughter of acclaimed crime writer James Lee Burke, she graduated with distinction from Stanford Law School, completed a judicial clerkship with the Ninth Circuit Court of Appeals, and serves as a legal and trial commentator for various radio and television programs. She lives in New York City with her husband and their french bulldog Duffer.

