Strong Silent Type - The Darkness 2
As soon as you get off the car, check the back of the truck in the corner to find the first relic of the mission.
The Brothers of Men
Go inside the club and search for Venus. Just follow the path and she'll come to you eventually. Continue following her until you reach her room.
Follow the path and kill the guards until you reach the objective point. Ask your darkling to climb up the vent and you'll be able to see what he sees. Continue moving forth until you reach an empty room. Approach the guard and execute him then continue head to the next corridor. Since you have to avoid the light, climb the pipe and move through the ceiling until you reach another room. Kill the guard and destroy the electrical panel.
A day in the life of a darkling
You'll be back in Jackie's control so destroy the panel to completely open the door. Check the first room to find some weapons, ammo and a talent shrine. Use it as necessary.
Approach the closed door and enemies will barge in. Kill them then grab the last relic in this mission.
The Key of Mictlan
Open the locked door and continue upstairs while taking out the lights. Once you reached the upper floor, continue killing the enemies. Follow the path until you reach a suspicious room with several generators. You won't have any choice but to get captured. Chapter ends.