Every season of Arrow has featured a major villain, some grand architect behind it all, the one pulling the strings and bringing about whatever evil is threatening Starling City that year. In season 1 there was Malcolm Merlyn, season 2 had Slade Wilson/Deathstroke, and last season's "big bad" was Ra's al Ghul.
This season that role is being played by Damien Darhk (Neal McDonough), and while characters like Deathstroke and Ra's pushed the limits of what humans could do, Darhk crosses that line, displaying abilities that are undeniably magical in nature. Call it The Flash effect if you will, but where Arrow initially stuck with the more grounded, street-level villains in its earlier seasons, the series has now gone full-blown comic book: meta-humans, magic powers, resurrection--it's all game now.
Trying to keep it together while the city around him goes crazy is Captain Lance, a long time skeptic of the supernatural and distrustful of vigilantes. But this season sees Lance form an uneasy alliance with a man he believes could save his city - Damian Darhk! The reveal that Lance is in cahoots with Darhk was a shocking one, but his reason for sticking with such a dubious ally aren't all that surprising: his family.
In our recent interview with Arrow actor Paul Blackthorne, he shared why Lance would continue working with as dangerous a dude as Damian Darhk:
"With regards to the relationship with Dahrk, after all the attacks and The Arrow being gone, Lance did what he thought would be the right thing for the city, and Dahrk was selling himself as that person – the guy that just wanted to help the city. Then, obviously, Dahrk went dark with his actions and intentions, which is when Lance started feeling uncomfortable about it. So, this is the point where Lance is trying to step back, but then, of course, Dahrk threatens Laurel and ends up in a tight corner. And, of course, how this plays out we’ll be seeing in the next few episodes. Initially, he was doing it for the right reasons, but it’s certainly been pretty awful for him in seeing Dahrk has turned into a monster and that now he can’t go back on his relationship with the man because he’s threatening Laurel. So, he’s in a tight jam."
After having lost a daughter, learning she was actually alive, then finding out she died again for real, it's understandable why Lance's top priority would be protecting what little of his family remains; namely, Laurel. He and Laurel may have had their differences over the years, and her lying to him about Sara's death was huge blow to their relationship, but as any father could attest, there's isn't anything he wouldn't do for his daughters. Even making a deal with a real devil.
As for how that relates to his other daughter, Sara, well, that's another tough situation. When faced with his newly resurrected but deranged daughter, Lance takes great pains considering whether it'd be best to simply put her down - something his pal Darhk even suggests. But though she may act feral and wild, in the end she's still his daughter, and keeping her safe will always be his number one priority.
But it isn't only for the sake of his daughters that he'll continue working for Darhk, but for the sake of his city. After the event's of tonight's episode, Lance and Oliver are finally back on the same page at to what's best for Starling City - defeating Darhk. And to do that, Oliver needs eyes on the inside; specifically, Lance. It'll be a fine line for Lance to walk, but as Blackthorne says, "he's in a tight jam."
Arrow airs Wednesday at 8/7c on The CW.