This section of Call of Cthulhu guide describes Chapter 12 - another one titled Darkwater Port. The main protagonist gets out of prison, however, the town is overrun by frantic citizens forcing Edward Pierce to use firearms to defend himself.
Reach the whaling station
This chapter begins when Officer Bradley visits the main protagonist and releases him from jail. After a while, Bradley will be eaten by the madness that has taken over the entire town. He won't be able to fight it. You have a choice - ease his suffering and shoot him, or leave him. Saving Officer Bradley allows you to unlock the Farewell achievement at the end of the game.
Decide on the policeman's fate and leave the jail. You will find yourself on a street at Darkwater port. Here, you encounter a group of mad townspeople - similarly to the sequence with Cat from the previous chapter, if you come in contact with them, you die. Thus, you have to either avoid or kill them. If you kill 5 mad townspeople, you get the Abomination of Darkwater achievement.
Note - remember that your weapon has a limited number of bullets. Try shooting from up close in order not to miss and, if possible, avoid killing by sneaking past the enemies.
Continue along the street until you reach a wounded policeman lying on the ground - he will give you several additional bullets. Get cross the street to the captain's office that you visited at the beginning of chapter 2.
While on the ground floor, investigate the map on the table - this will activate a reconstruction. Other objects to examine are the plate on the table, Dr. Fuller, Charles Hawkins, CPT. Fitzroy, and Sarah Hawkins. After the reconstruction, a short cutscene will start.
After the cutscene, go upstairs, where you will find wounded Cat. She will offer you help with getting to the whaling station provided you bring her a first aid kit. It can be found at warehouse 36 - the one you explore in chapter 2.
Leave the building and go towards the bay - the place where you could find a bottle of liquor during chapter 2 in order to get to the warehouse. You will find wounded Mitchell (the bar owner) at the end of the bay. He will also offer his help in return for healing. Additionally, if you bring him the first-aid kit, you will unlock the Good Samaritan achievement.
Now, go to warehouse 36 to get the first aid kit. You can get there using the passage that was guarded by a band of thugs in chapter 2. In the warehouse, there is a madman - kill him and take the first-aid kit from the table to the right from the entrance. Now, you have to decide who are you going to help. The choice is purely "cosmetic" - depending on your decision, you will enter the station from a different side. If you want the achievement - choose Mitchell.
Now, reach the whaling station - it is a cloistered area. There are many dark locations where - you can use that to hide from your enemies and not waste ammo.
Go through the narrow passages - you can't get lost here, as there is only one way. There are no collectibles either - so you don't have to look for books hidden in the corners. Continue forward until you reach metal stairs. Climb them upstairs and enter the whaling station to finish this chapter.