"Three Ghosts" is the 9th episode of the second season of Arrow. It aired on December 11, 2013.
After a fight with Cyrus Gold AKA the Acolyte, Oliver is drugged and left for dead. Determined to cure him, Felicity makes a risky decision. The cure causes Oliver to hallucinate, and what he sees forces him to confront his past. Meanwhile, Barry continues to help Felicity, and their connection grows stronger. The Arrow asks Lance to look into Gold, but when the stakeout on Gold goes bad, someone gets killed. Roy is captured and tortured by Brother Blood.
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- The three "ghosts" who appear to Oliver are a reference to Charles Dickens' A Christmas Carol. In following this, Shado is that of the past, with Slade representing Oliver's current self doubts, and Tommy finally offering redemption and a future for Oliver.
- Slade in the present day has an eye patch and his hair appears to be greying, both elements which are usually present on Slade's character.
- The scene at the end where Barry gets struck by lightning will later be used in the Pilot episode of the spinoff series The Flash.
- Reporter "Linda Park" is a reference to the third Flash Wally West's wife, who would later appear in person on The Flash.
- This is the only episode in the Arrowverse that include both Colin Donnell and Grant Gustin.
- In one of the relatively few direct references to her Judaism, when Barry asks what Felicity will be doing for Christmas she replies, "Lighting my menorah."
- This episode talks about the English nursery rhyme, "Solomon Grundy", stating that it's about the seven stages of life.
- When Oliver hallucinates Slade and tries to fight him and cannot touch him, it strongly references the animated series the Teen Titans episode: "Haunted" in which Robin hallucinates Slade (which has been caused by a chemical reagent) and tries to fight him to which Slade is not there due to him died in the season 2 finale.