Saboteur

There are two threads to my story.
One thread narrates the last voyage of the Mont Blanc, one of the ships involved in the Halifax explosion of 6 December 1917. This was the largest man-made explosion in the world before Heroshima.
The other thread follows a Canadian-German saboteur who blows up ships leaving Halifax in 1916 and 1917 by secretely planting small "cigar" bombs in the holds of out-going ships. Bombs with delayed triggers that explode days later far out to sea. He is supported and well trained in his activities by a German ring of American-German saboteurs under direct control by Germany. He is supplid with cigar" bombs made by a German-American pharmacist from a factory in New Jersey. His final mission directed by his American handlers is to blow up the Mont Blanc.
The two threads intertwine on 6 Dec 1917.