The Dark Tunnel

Blurb

The Dark Tunnel is a 1944 spy thriller novel written by Kenneth Millar. For this novel, his debut, Millar used his real name -- he is generally better known as Ross Macdonald.
University professor Robert Branch makes light of his best friend's suspicions that there is a Nazi spy in their sleepy, midwestern university town. He is more interested in the fact that his ex-girlfriend from Germany is about to take a post at the university. But then his ex turns out to be rather mysteriously engaged to the son of the German professor and he watches his best friend fall to his death out his own office window. Robert is the only one who thinks it is not suicide. When he attempts to expose the killers, he is not believed and he finds himself running for his life, marked as their next target.
Millar wrote The Dark Tunnel in one month at Ann Arbor in 1943, while completing graduate work at the University of Michigan.
This book was reprinted by Lion in 1955 under the title I Die Slowly.
The book, under both titles, is currently out of print.