The Apartment Next Door

This is a WWI early espionage novel set in the United States. Without a central information gathering network, intelligence was collected separately by the Departments of War, Army, Navy, State and Treasury, each operating independently of the others. When a young woman is recruited to keep tabs on suspected German agents in the apartment next to her own, without the knowledge even of her parents, the suspense is ratcheted up, as a weird spy chase begins...