During King Richard's crusade, Ali ben Azra, one of the hated Saracens is captured and brought to England. In their turn, the Saracens capture Lord Rossmore and hold him hostage against Ali's safe return. Plans are made for the exchange, but Sir James Rossmore, nephew of Lord Rossmore, has other ideas. He has devised a plot that will enable him to inherit his uncle's fortune, placing the blame on the innocent Ali ben Azra. Robin decides to intervene.