Dive into the thrilling world of Mahmoud Salem's iconic 'The 13 Devils' series, a beloved cornerstone of Egyptian youth literature. In 'The Secret of the Unknown Submarine,' the intrepid team of young heroes faces one of their most perplexing challenges yet. A mysterious, untraceable submarine poses an unprecedented threat, lurking in the depths with unknown motives. As the 13 Devils race against time, they must unravel the enigmatic origins of this underwater menace, encountering suspense, danger, and unexpected revelations. This particular volume, Number 260, promises a classic adventure filled with Mahmoud Salem's signature blend of intrigue and daring escapades, captivating young readers.