An upcoming episode, titled 'Haunted,' of season 4 of Arrow has been leaked online preceding its official television air date.

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The episode is highlight as John Constantine (Matt Ryan) makes his appearance with the mission of resuscitating Sara (Caity Lotz). According to a Deadline report the episode was uploaded on Torrents on the night of Nov. 1, three days before it would hit TV screens. This has been a very highly anticipated episode as it was to be the special Arrow/Constantine crossover.

In the episode, Oliver (Stephen Amell) will reach out to Constantine to help deal with the new Sara, after her experience in the Lazarus pit. It had been revealed that Sara will have to pay in some way for being brought back to life as the Lazarus pit has some grievous side effects. In the previous episode, titled 'Restoration', Sara's plight was made known.

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In fact some reports went as far to suggest that Sara might lose her humanity, so Constantine's assistance would be key.

Here's the official synopsis:

"MATT RYAN REPRISES HIS ROLE AS JOHN CONSTANTINE ON ARROW - When things take a turn for the worse with Sara (guest star Caity Lotz), Oliver (Stephen Amell) calls in a favor from an old friend who deals in the mystical, John Constantine (guest star Matt Ryan). John Badham directed the episode written by Brian Ford Sullivan & Oscar Balderrama."

'Haunted' will air on Nov. 4 on The CW.

Watch the preview: