"Arrow" characters John Constantine (Matt Ryan, left) and Oliver Queen (Stephen Amell, right) will join forces in Season 4, episode 5 as the former NBC hero comes to Star City and the CW. CW

It’s going to be a unique week for the characters on the CW series “Arrow” as the group seeks outside help to bring one of its most beloved members back to life. In the wake of the startling events from last week’s episode, Team Arrow will need to set science and technology aside and embrace the mystical in the first crossover event of Season 4 in episode 5, "The Haunted."

Now that Sara Lance (Caity Lotz) has been resurrected from the grave and returned to Star City, things aren’t all sunshine and rainbows. As has been explained to the characters time and time again, bringing someone back to life by way of the Lazarus Pit is a difficult task. For someone who was dead as long as Sara, it can only succeed in resurrecting the body without its soul. Still, thinking she could find a way around that problem, Sara’s sister, Laurel Lance (Katie Cassidy), thought she could keep the super-strong monster version of her sister locked up in her apartment building’s basement. She couldn’t and now Oliver (Stephen Amell) needs help to stop her from going on a rampage that could cost innocent lives.

“Things take a turn for the worse with Sara, as Oliver calls in a favor from an old friend, John Constantine, who deals in the mystical,” reads the episode’s official TV Guide plot synopsis.

As previously reported, the former star of his own NBC series, Matt Ryan, will reprise his role from the canceled drama for a one-time crossover event. Both “Constantine” and “The Green Arrow” exist within the world of DC Comics, so the crossover isn’t as out of left field as it sounds. Still, for a show that often grounds itself in reality, the light introduction of magic and the supernatural in Season 4 is about to come to the surface in episode 5 as the characters are forced to acknowledge powers outside their understanding. Hopefully Constantine will also be able to gives viewers some answers as to what can stop the new principal bad guy, Damien Darhk (Neal McDonough).

In a clip for the upcoming episode, posted below, it is revealed that Oliver and Constantine apparently have a pre-existing relationship, as the archer calls upon the paranormal demonologist for help once he discovers the secret that Laurel has been keeping from him. While Constantine isn’t expected to be in any episodes other than this one, it’s possible we’ll see both the character’s modern-day exploits in Star City as well as be treated to some background information as to how he and Oliver met -- perhaps in this season’s flashback storyline to the island of Lian Yu.

Fortunately, fans won’t have to wait too long to see how the “Constantine”/”Arrow” crossover takes shape as it airs Wednesday, Nov. 4, at 8 p.m. EST on the CW.

Are you excited to see John Constantine join the mix? Comment below or tweet your “Arrow” thoughts to @TylerMcCarthy.