Robin Hood will pitch his skills on the bow and arrow against the Wicked Witch and her spells, according to the episode 18 spoilers for "Once Upon a Time" season 4. Meanwhile, where has the author ran off to?

"The ABC series' next new episode, 'Heart of Gold,' airs April 12 and marks the return of Rebecca Mader as the Wicked Witch, while Sean Maguire puts in another appearance as Robin, who seems to be working "undercover" here, in flashbacks, as an Oz palace guard," TVLine said.

Cartermatt noted that the promo teased after Sunday's episode "Best Laid Plans" hinted that the Wicked Witch is already back in the present and "more powerful than ever."

"But the only way we could presume that is taking place is via some sort of uber-powerful spell. Who does it benefit to see Zelena back in Storybrooke? The answer is really 'no one.' Given that Rumpelstiltskin killed her, he's not chomping at the bit to see her again."

In the last episode, the author (played by Patrick Fischler) appeared in the enchanted forest once again. But he immediately scampered away after Emma released him.

There's no synopsis yet for "Once Upon a Time" season 4, episode 18 but the Wiki entry revealed the guest stars for "Heart of Gold," which include Sean Maguire as Robin Hood; Patrick Fischler as Peddler; Christie Laing as Maid Marian; Jason Burkart as Little John; Wil Traval as Sheriff/Keith; Kristin Bauer van Straten as Maleficent; Victoria Smurfit as Cruella De Vil; Merrin Dungey as Ursula; Rebecca Mader as Wicked Witch of the West/Zelena; and Raphael Alejandro as Roland.

This episode is written by Scott Nimerfro and Tze Chun and will be directed by Billy Gierhart.

Watch out for more "Once Upon a Time" season 4, episode 18 spoilers which will be published here ahead of the airing date on April 12 on ABC.