FBI forensic psychologist Abby Chilton thought she would be content to analyze agents and ensure they pass through her gauntlet of psych tests. She left field work for the peace and politics of the office. The only problem is she doesn't like peace and hates politics. Two men enter her boring life. One is an Interpol agent. The other is a killer. Both men have plans for her. Both men have a shared past. Neither one will let her stay behind her safe and secure desk. Neither one know what they have done. Abby joins forces with mysterious Interpol Agent Jonas Lange to profile and track the most dangerous killer either of them have ever encountered. The Observer has the skills of a profiler and the soul of a remorseless killer. Abby must decide between falling for Lange or shooting him. The Observer must struggle through the same decision about Abby.