Excelsior Exchange interweaves episodes of espionage and betrayal to tell the stories of John Osaka Oman and Sam Yang, two men who are vying to gain control of nuclear secrets. John Osaka Oman is an agent his government believes to be a traitor; Sam Yang a respected Oxford don and nuclear scientist. Through assassinations, desert warfare, and the frighteningly real conflicts in Afghanistan, Pakistan and Iran, the story builds towards a chilling climax: who are these men, and to what lengths will they go to get their hands on classified information that could ultimately bring about the end of the world? A pair of British Colonels attempt to track down both Osaka Oman and Yang, to unmask the real traitor in order to gain control over terrorist groups and halt the threat of nuclear war. Osaka Oman orchestrates Yang's assassination and that of Secretary-General Addai Mushra of Iran as a political embarrassment, and it is never clear for whom he really works. But when Yang's body is set to be cremated, Osaka Oman receives instruction to identify the body. Osaka Oman realizes he's got the wrong man and is left to wonder what happened to the real Sam Yang - who is alive and working to create nuclear weapons. The story involves several mercenaries who continue throughout the story to be involved in several covert operations into various countries where the sabotage of nuclear equipment is attempted to halt or slow down a countries nuclear enrichment.