Heinrich Heinrichson is an adventurer and a top agent for the Tomas branch of the Cahill family. He is an expert Clue hunter who visits extreme locations (such as the Amazon rain forest, the Gobi desert, and the Arctic) in search of Clues. He may have received a hint regarding the Janus Clue, Silk, hidden in Nepal, as he visited Mount Everest, where the Clue is hidden. Other Clues he may have pursued include Phosphorus and Blood, as postcards from Loch Ness and the Eiffel Tower were found on his person after his arrest.
Heinrich's activities seem to be particularly tied to the Lucian branch. In addition to his visit to Paris, a Lucian stronghold city, he gathered intel on Lucian branch leadership, discovering that the branch was led by Vikram Kabra. Lucian agent Irina Spasky tracked Heinrich from Nepal to Sydney, Australia, where he was arrested after causing a dispute with a tourist. The Lucians were able to acquire Heinrich from the local police and held him captive indefinitely.