Side note! In the comic books, Slade Wilson is the real name of Deathstroke, the dude with the two-color mask that shoved a sword through Oliver's torso. And this guy does have two swords.
Modern-day. Detective Lance is on a rooftop and Oliver appears behind him in his hood. Oliver blusters a little and Lance tells him he needs him. Oliver acts tough: "He'll kill her anyway. So why come to me?" Well, there's no one else he can trust. Oliver says he can't take the mansion by himself. Lance says he needs Oliver's help. Oliver answers, "Then I need yours." Just like it requires two people to take an airfield it takes two people to assault a killer's well-fortified house. I guess.
The mansion has armed guards. Cyrus probably got some new ones after the last ones got arrowed. He holds a knife to Laurel's throat and she promises that he's going to prison for life. Cyrus talks about how many bullets these machine guns can fire. And we see Oliver kill four or five guards. Cyrus brags about his sharpshooters, but Oliver kills them too. Cyrus mentions his "veritable army of sons-of-bitches" and then we see Oliver killing a bunch of them, too. Cyrus says that the Hood carries 24 arrows and flechettes. Oliver comes in and lets himself be taken prisoner. Wait, so his plan was to have exactly 24 guards, because then Oliver would be out of arrows when he got inside? That's kind of brilliant. Although it does appear to mean that Oliver killed two dozen people just now. So now Oliver's helpless. Until! Detective Lance comes in and shoots another couple of guys. He's about to shoot Cyrus, but Oliver shoots the gun out of his hand. "I'm the vigilante; you're the cop." But Lance still punches Cyrus before arresting him. So I guess the reason Oliver needed help was that he knew he'd be out of arrows, and he needed someone with a gun as backup? That's crazy. Plus why couldn't he use Diggle?
Police station. Lance is going to take Laurel home, but she would like to take a cab. She wants him to stay away from him because she can't trust him. She's still mad about being used to set up her beloved vigilante.