More recently , he has written a series of short novels for young adults that are available in Kindle books . Set in the early 1950s , the books involve boys investigating a series of mysteries , such as the disappearance of a former OSS agent , an ancient Native American curse , and a character linked to Unit 731 . All are freestanding and take place in both a rural Pennsylvania setting and New York City
Unit 731
Unit 731
John S. Marr