On this page of our guide to Desperados 3 you can find the first part of walkthrough of mission 4 - Until Death Do Us Part. In this part of the mission you can only take control of Kate. Our guide explains how to get inside the Higgins estate and how to sneak into the mayor's office without being noticed. Once she's in the office, Kate will have to search the desk.
In our walkthrough of mission 4 there are references to the map included in the world atlas, which you will find on the first page of this chapter. For example, a marking (M4,5) indicates that you should find the blue point with number 5 on mission map 4.
You start the mission by playing as Kate (M4,1). The heroine has access to the gardens around the property and you don't have to sneak around. Don't attack neutral characters around the building, because Kate doesn't have a rope to tie up stunned people. The attacked character will therefore inevitably return to full strength, although if Kate wasn't noticed when the kick was made, no alarm should be triggered. The NPCs, after "waking up", will simply return to their former activities.
Head north, that is, towards the area where the maid with the key is walking (M4,3). Don't attack her right away, because the neighborhood is watched by an opponent in a poncho standing on the balcony of the property (M4,2). Read the new tutorials and throw a vial of perfume at your opponent on the balcony. The enemy will be temporarily blinded. Fortunately, the perfume is an unlimited gadget and even if you miss it, you can use it again after it gets renewed.
Quickly get close to the maid, enter interaction mode (press CTRL - PC version) and click on the woman to rob her and get the key. You have to do it before your opponent on the balcony gets his eyesight back. Head to the east gate with the key. Opening it will unlock your access to the new part of the estate, although you don't have to sneak in here because Kate still has the right to stay here.
You must reach the side entrance to the property (M4,4). Don't try to break into the building right away, or it'll alarm the characters that reside nearby. Throw the perfume at a remote guard and then kick the worker standing at the door. Only after stunning both these characters quickly click on the door to open the lock. Again, you don't have to worry about the alarm. After the guard and employee have returned to full strength, they should remain in the places where they originally stood.
Hide behind any large obstacle in order not to be noticed by the guards from the corridor (M4,5). Notice that one of them is patrolling the corridor. Wait till he stops by the right guard to talk to him. Throw a vial of perfume at two guards and then start running down the long corridor to the office entrance (M4,6). On the way, you'll pass a guard with his back turned, and unless you touch him he shouldn't be alarmed.
Open another door leading directly to the office. Click on the desk to launch a cutscene (Kate will hide in the closet). In the next part of the mission, you will take control of Cooper himself.