In 1920, Hynd joined The Boston Post as a general assignment reporter. Over the years, he covered and published more than 1000 crime cases for newspapers in Boston, New York, New Jersey and Philadelphia.

He contributed to magazines such as The Reader's Digest, Liberty, True, The Saturday Evening Post, Colliers and Look, as well as 'pulp' true crime magazines True Detective, True Police Cases, Master Detective, Official Detective and others.

In 1943, Hynd wrote two wartime NY Times Best Selling books, Passport to Treason and Betrayal from the East about German and Japanese espionage activity in the US during the lead-up to World War Two. Other non-fiction works followed, predominantly true crime.