Head on to fight several Mays. There are quite a few of them here, once they've all been defeated, you'll walk out of the sewers.

You'll then arrive at the factory entrance. Along with the usual Skull Cross guys, you'll also encounter a new member here: Hunter. He's slow to move, but he does have a slide kick, and can also hit you with his baseball bat. You'll face a few of him here, along with some of the weaker gang members. After beating them all, Fritz and his clones will come on, so be ready to defeat them or avoid their grenades.

Head on to fight even more Hunters, along with some other enemies like Ray and Joe. Head right and be ready to deal with Fritz and his clones again.

Once you reach the factory entrance, a few more enemies will come on from the left, which include Andore and Hunter. Defeat them and you'll then break down the door, and enter the factory. Fight the first wave of enemies you come across, which are Billy, May and Hunter. Throw one of them across the door in the background.

This will break the door, so head up and go into the room. There are a few enemies in here, you can leave the room at any time be heading back the way you came in. However, there is a hidden extra life in the bottom right corner, so pick that up first. Head back out and resume going down the corridor, where more Skull Cross gang members are waiting. There is another alternate route choice you can make here, involving the door in the background. Throw an enemy over it to break it open, or keep going right.