Visiting his family in Melbourne for the passing of his aunt, Warren unearths a letter sent to his late uncle during the Spanish civil war. Driven by curiosity, he follows the letter all the way to England where he encounters a couple of undergraduate historians who strangely enough had been conducting research connected to the letter. They soon crew up and embark on a story hunt taking them halfway around the world, and with the help of an infamous assassin and other quaint characters they meet along the way, uncover an allegiance that remains ticking after 70 years.

Weaved in historical events, Allegiance in Arms is an intriguing story that brings together the past, the present, and an unusual friendship that transcends countries, conflicts, characters and perhaps ... oneself?