The Moon Man was a mysterious adventurer who only went out "on nights when the full moon shines". He was independently wealthy, lived in a penthouse and was reportedly a "master of many sciences".
In his first known case, he investigated on the poisoning of 35 orphan children by contaminated food delivered at their orphanage. He suspected Boss McGool, a local criminal mastermind, was responsible. The Moon Man visited Nadia La Sanne, secretary to McGool, at her house. He scared her to the point of fainting and then stole her handbag. He found within receipts proving McGool had bought cheap meat. Connecting him to the meat delivered at the orphanage.
He visited McGool at his place and beat up a couple of thugs. He threatened McGool but left with no further incident. Only to go to Nadia again, manhandling her until she signed a written confession. He then returned to McGool's office ... to find him long gone. He noticed the Boss to have marked a certain train in a railroad schedule. The Moon Man then "brilliantly" deduced this is how the Boss planned to escape. So he boarded the same train, jumping inside and scaring the passengers. He knocked out the Boss and held his thugs at gunpoint. He then jumped off the train with the unconscious Boss, dragging him to the nearest police precinct. He returned to his penthouse, never to be seen again.