In the Green Arrow comics, Black Canary is frequently both the hero's crime-fighting partner, and his love interest. They even had their own book series, Green Arrow and Black Canary, in which they were married. So when Arrow first premiered with Laurel Lance as Oliver Queen's ex-girlfriend, fans knew it was only a matter of time before she took on the role. In season 3, Laurel did just that and became Black Canary. It was not a smooth journey, she needed a lot of training and Ollie initially didn't want her suiting up at all - but she eventually became an integral part of the team. That is, until late in season 4, when she was fatally stabbed by Damien Darhk.
Laurel's death has had a major impact on the show. As mayor, Ollie had a statue of the Black Canary made. As the Green Arrow, he considers what Laurel would want when he makes all kinds of decisions, everything from whether or not to kill to taking on new recruits. And he's not the only one who is affected by her loss, Thea has retired from being Speedy (mostly) and Quentin Lance has relapsed in his alcoholism. Still, the team seemed to finally be moving on with their lives. Until the last moments of the midseason finale, when Ollie found Laurel, alive and well, in the Arrowcave.
EP Marc Guggenheim was asked by EW about the recent Arrow promo that shows a rather villainous Laurel attacking the team. He declined to comment, but when asked about her future, did offer a bit of a tease:
"The episode ends with laying a very specific seed with a very specific game part on our part that we hope to see come to fruition."
Perhaps that seed has something to do with the contract actress Katie Cassidy signed, making her a regular on all four Arrowverse shows. John Barrowman and Wentworth Miller both signed similar contracts, and now Barrowman's Malcolm Merlyn is a member of The Legion of Doom on Legends of Tomorrow with Miller's Leonard Snart lined up to join. Perhaps that is also the plan for Laurel Lance.
There is also the popular theory - that was seemingly confirmed by the midseason premiere promo - that Laurel is indeed dead, and this version of her is from another world in the multiverse. It seems she is the Earth-2 Laurel, a villain who used the name Black Siren. The last time Black Siren was seen, she was being locked in the pipeline on The Flash, though it is possible she escaped. Or maybe due to Flashpoint, she was never captured in the first place. Backing up this theory is the shot in the promo where Laurel uses her canary cry. As Black Canary, she needed a tricked out collar to use the cry, whereas Black Siren was a metahuman who could do it naturally.
Arrow season 5 returns to The CW with ‘Who Are You?’ on Wednesday, January 25 at 8pm.