'Arrow' season 5 return date, spoilers: New promo featuring Laurel Lance resolves major midseason finale bombshell

The CW has just released a new promo teaser for "Arrow," and it reveals a lot about the major cliffhanger from the show's midseason finale.

Episode 9 left off with Oliver (Stephen Arnell) accidentally killing Felicity's (Emily Bett Rickards) new boyfriend, Detective Billy Malone, after Prometheus manipulated him. Towards the end of the episode, Oliver was surprised to see Laurel Lance (Katie Cassidy) waiting for him. Aside from being dead since season 4, Laurel's return is not possible since the Lazarus pits, which is the only known way to resurrect people from the DC universe, have already been destroyed.

In the latest sneak peak from the network, Team Arrow and Laurel make a toast to celebrate their new victory. Things take a turn for the worse when Laurel lets out a loud, scream which makes Oliver realize that she's not the person he used to love. "Finally, it's about time someone figured it out," she says as she walks towards Oliver and Felicity.

As io9 points out, the character who returned in episode 9 is an evil Laurel. This presumably means that she is Earth-2's Laurel Lance, a supervillain who is also known as Black Siren. She made an appearance on "The Flash" earlier this year, but how she ended up in Earth-1 remains unclear. Given that there are a number of evil speedsters who can alternate realities around the DC universe, it's highly possible that one of them picked Black Siren up and dropped her off in Star City. Unfortunately, fans would have to tune in next year to know why the nefarious character came back.

Speaking with TV Line, co-showrunner Wendy Mericle shared some details about the upcoming episode. "It's a familiar face, someone he loves and is very happy to see, and now she's back in the flesh, so it's a very welcome surprise," she hinted. "And yet as we often say, 'nothing is really ever as it seems.' There will definitely be a 'dark silver lining' when Oliver finds out what's really going on," she went on to say.

The fifth season of "Arrow" premieres on Wednesday, Jan. 5, at 8 p.m. ET on The CW.