Due to poor ratings, this is the final episode of the series. An online petition, which received upwards of 50,000 signatures was started to encourage other networks to pick up the series, to no avail. There is however, a script online, by the show' s creator, for a 14th episode.
Based heavily on the story 'Waiting for the Man' originally published in Hellblazer #4.
The story this episode is based on was the introduction of Zed, in Hellblazer #4.
The next episode (the 14th) was never actually aired on TV. However, the script was released by writer Daniel Cerone. Trying to promote the crossover with Arrow, he tweeted, "To boost #Arrow, if this hits 2k retweets I'll post script for what would'a been ep 14 of #Constantine." The tweet easily made that goal, and the script was then released.
The branding iron the man is heating up is called the sigil of Lucifer.