They came to Standedge Tunnel, the longest canal tunnel in England. Six students go in, and two and a half hours later, the boat reappears on the other side with only one of the students, unconscious, and the dog. Five years later, the case of the Standedge Six has faded from most people's memory. The police investigation concluded that the only remaining student killed his friends, hid the bodies on the boat and then returned to move them to an undisclosed location. In prison, the last student allegedly killed himself, which the police took as a confession. But some don't think the mystery is as easy as that. Ron Ferris, a middle aged and jaded journalist, who is grieving after his wife goes missing, decides to write a book about the Standedge Six. What first he thinks of as a mere cash-grab quickly becomes more personal as he sees similarities between the students' and his wife's disappearance. Ferris sees the case from every angle - the law, the conspiracy theorists, the supernatural cultists. But what is he really searching for? And do the answers he's looking for lie deep within the darkness of the tunnel?