Although terrorism was suspected, given a number of terrorist threats against American citizens (most on board the flight were Americans), mechanical failure could not immediately be discounted. This article traces the investigation and its findings step-by-step, including the contributions of the investigative resources of various countries. Investigators learned many lessons from their experiences. Information sharing and cooperation among investigators in a number of countries was vital. Separately, neither the police in Scotland nor the FBI would have been able to solve the case. The efforts and resources of the intelligence services of each country were essential for obtaining and interpreting the evidence necessary to identify suspects and eventually obtain a conviction of the Libyan intelligence officer who planned and coordinated the bombing and murders of all aboard the flight. Keeping investigators motivated for the lengthy period of the investigation was difficult. Motivation was maintained by two photographs on the wall at the FBI’s Washington Field Office, one of a baby shoe (there were 16 children under 10 years old on the plane) and a second photo of the tail of Pan Am Flight 103, which had a decal of an American flag. In the office of the Senior Investigating Officer in Scotland was a large poster board that had the names and identifying information about the 270 victims. A key to the investigative method was attention to detail. If an investigator had overlooked any fragment of evidence from the dispersed remains of the plane, the case could not have been solved.