Exciting mystery enters naturally into a fine story about the siege and capture of loyal Boston colonists of Louisburg on Cape Breton Island in the mouth of the St. Lawrence, thirty years before Bunker Hill. Young Caleb whose people are shippers, is well aware of the danger from French attacks on colonial merchantmen. One evening on his way to help loading at the wharves, he finds a map showing French gun placements. After telling Col. William Pepperell, Caleb goes with the Colonel's troops as drummer boy, to the successful attack at Cape Breton. Subsequently, Shubael a familiar Boston marine supplier is found a traitor. Good historical fiction and some startling perspectives in Harve Stein's illustrations add drama.