When Ralph Black, chain store magnate, was found shot by his own gun in his locked library, the New York police pronounced it as suicide. However, family members believe it was murder. His sister in England, Maria Black, M.A., Headmistress of a girls' school, wants to discover the truth. She travels to America, and with her penchant for solving crimes, sets to work to trace the mysterious plot against her brother to the final unmasking of the amazing truth.