Sherlock Holmes and The Portal of Time by Michael Druce
Only one man can change the outcome of World War II—Professor Moriarty. And only one man can stop him—Sherlock Holmes. In a breakneck race through time, Holmes and Watson must follow Moriarty eighteen years into the future to prevent him from helping the Germans develop the atomic bomb. With the fate of the world hanging in the balance, Holmes and Watson join forces with H.G. Wells, his wife Jane, and Albert Einstein in a life and death struggle on the eve of World War II.