When the enterprising cybercriminal Eric Eoin Marques pleaded guilty in an American court this week, it was meant to bring closure to a seven-year-long international legal struggle centered on his dark web empire. In the end, it did anything but. Marques faces up to 30 years in jail for running Freedom Hosting, which temporarily existed beyond reach of the law and ended up being used to host drug markets, money-laundering operations, hacking groups, and millions of images of child abuse. But there is still one question that police have yet to answer: How exactly were they able to catch him? Investigators were somehow able to break the layers of anonymity that Marques had constructed, leading them to locate a crucial server in France. This discovery eventually led them to Marques himself, who was arrested in Ireland in 2013. Marques was the first in a line of famous cybercriminals to be caught despite believing that using the privacy-shielding anonymity network Tor would make them safe behind their keyboards. The case demonstrates that government agencies can trace suspects through networks that were designed to be impenetrable.