Warren William is the Lone Wolf, Michael Lanyard, in "Counter Espionage" from 1942.
Michael has the difficult assignment of stopping German spies from stealing valuable information from the British government. That's the Mcguffin, of course.
The police suspect Lanyard of actually working with the Nazis.
Eric Blore provides the comic relief, and Hillary Brooke is the suspicious daughter of a murdered man who had these important plans in his safe.
I love Warren William, so it's always great to see him. Look for Lloyd Bridges in an uncredited role as a waiter, and Forrest Tucker has a small role.