The Tourist (Milo Weaver, Bk. 1)

Milo Weaver has tried to leave his old life of secrets and lies behind by giving up his job as a "tourist" for the CIA - an undercover agent with no home, no identity - and working a desk at the CIA's New York headquarters. But staying retired from the field becomes impossible when the arrest of a long-sought-after assassin sets off an investigation into one of Milo's oldest colleagues and friends. With new layers of intrigue being exposed in his old cases, he has no choice but to go back undercover and find out who's been pulling the strings once and for all.