Percy F. Westerman wrote "The Mysterious Ship,". The plot centers on the exploits of two young friends during World War I. They observe a mysterious ship that resembles a German submarine but is far bigger than any submarine they have ever seen. They inform the authorities of their sighting, but they are not taken seriously. After their own inquiry, the two pals learn that the ship is a component of a Nazi scheme to obstruct British commerce channels. To find the mysterious ship and stop it from doing further harm, they team up with the British navy. They face many challenges and failures along the road, but they finally complete their purpose. Two young boys' fortitude in the face of peril and misfortune is highlighted in this page-turning story of adventure and velour. Also, it offers a look into the British attempts to defend their maritime routes during World War I as well as the naval combat strategies used throughout that conflict.