SPOILER WARNING: This article contains spoilers for "What We Leave Behind," the mid-season finale of "Arrow."


Oliver Queen's life is about to become much more complicated. In "What We Leave Behind," the mid-season finale of "Arrow," he had a pretty rough time, but nothing could have prepared him for who he found in the bunker at the end of the episode: Laurel "Black Canary" Lance.

Yes, it's true: Katie Cassidy's Laurel Lance is back, but -- beyond that -- not much else is known about the character. After visiting Susan Williams for a pick-me-up, Oliver shuffled back to an empty Arrow cave, only to see a shadowy figure standing in front of the costume display. When Oliver barked, "Who are you?", Laurel turned around to face him and said, "Hey, Ollie" -- and that's where the episode ended.

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Since no one else was in the bunker at the time, it's hard to say whether or not Laurel was actually, physically in the room. Is she a vision triggered by the traumatic events he just went through? A doppelganger from a parallel universe? A product of time travel, or perhaps even Flashpoint? A robot? A shapeshifter? Unfortunately, those questions won't be answered until the show returns from its winter hiatus.

The episode was packed with other revelations as well. After Prometheus attacked Curtis near the mayor's office, Felicity's boyfriend Billy Malone began to look into the case, despite Felicity's protestations. As he discovered a photo of Justin Claybourne's illegitimate child, Prometheus kidnapped him, then lured Oliver to a warehouse set up like one of his hits from his Hood days. During the ensuing battle, Prometheus tricked Oliver by gagging Malone and dressing him in a Prometheus costume; Oliver fired off the killing blow, only to discover that he had killed Malone, not Prometheus. Though Felicity ultimately blamed Prometheus for Malone's death, the last shot of the episode found her crying alone on her couch.

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Thanks to Malone, Team Arrow discovered a few potential clues about Prometheus' identity. In his search, Malone stumbled across a baby photo, which apparently belonged to Justin Claybourne -- a name Oliver had crossed off his father's list during the events of Season 1. As it turns out, Claybourne had an illegitimate child, who would be about 30 years old now. This seems to be the first clue towards Prometheus' identity, and the evil archer played into that notion by setting up his victims in the same way Oliver left them the night Claybourne was killed. However, there was no verbal confirmation from Prometheus himself, so it's unclear at this time if that information was a red herring.

Additionally, Curtis' husband Paul found out that Curtis was working with Green Arrow and presented an ultimatum: choose vigilante life or me. Curtis seemed to all but make up his mind, only to find that Paul has made a decision of his own as the episode drew to a close. Curtis found him packing up his things to go stay with his brother, and he left a sobbing Curtis alone in their apartment.

Diggle wasn't exempt, either. He received a call that seemed to be from Lyla about their son JJ; "she" told him that JJ was sick, and he rushed to one of their safe houses, only to discover an entire SWAT team waiting for him. He raised his hands in the air as they all trained their rifles on him, and his scene concluded on that ambiguous note.

Starring Stephen Amell as the Emerald Archer, "Arrow" airs Wednesdays at 8 pm ET/PT on The CW. The series also stars Emily Bett Rickards, David Ramsey, John Barrowman, Willa Holland and more.