Tankers moving silently along the world's power lines look like ordinary merchant ships from the outside. However, this structure, called the 'dark fleet', is one of the most invisible and controversial networks of the global system. The findings that emerged on some ships, together with the claims that 'the secret network has been solved', have completely shaken the perception of security at sea. And the real detail that US officials say 'it made us lose sleep' is quite thought-provoking...