 There were five main storylines in the run . The first , collected as " Original <unk> " , deals with John travelling to America to <unk> a demon , <unk> , and investigate a strange cult known as <unk> 's Army , crossing paths with a demon called Nergal ( from whom he gains demon blood ) , and having to be responsible for killing an old friend , Gary Lester , and betraying another , called <unk> , in the process . The following four issues , " The Devil You Know " finally explain John 's failure to save a young girl , <unk> , from a demon in Newcastle , an event that left him near insane and incarcerated in an <unk> known as <unk> , and still haunted him to the comic 's end . He eventually discovers that the demon responsible for this was Nergal , and uses a technological scheme to trap him , and lead him back to hell . It also contains a crossover with Swamp Thing , where Constantine loses his body while the Swamp Thing uses it to <unk> . 
