Along Came a Spider (Alex Cross, 1) by James Patterson

Alex Cross is a homicide detective with a Ph.D. in psychology. He works and lives in Southeast D.C. and looks like Muhammad Ali in his prime. He's a tough guy from a tough part of town who wears Harris Tweed jackets and likes to relax by banging out Gershwin tunes on his baby grand piano. But he also has two adorable kids of his own, and they are his own special vulnerabilities.

Jezzie Flanagan is the first woman ever to hold the highly sensitive job as supervisor of the Secret Service in Washington. Blond, mysterious, seductive, she's got an outer shell that's as tough as it is beautiful. She rides her black BMW motorcycle at speeds of no less than 100 mph. What is she running from? What is her secret?