The Mysterious Woman
Our switch to Kelso starts off with a "mysterious" woman entering his office. Seems like a good start. Talk to Elsa and read through the letter that they sent her. Once you've read it, back out of it. Flip the paper over to the side so that you can read the entire report for the incident.
Once you're done, back out to talk to Elsa. Doubt the reason for the dispute, and doubt her connection to Lou. She is telling the truth about her motive though, so believe that.
Once she leaves, go up to Benson's Office. It's not far or hidden, so just go in and watch the cutscene. Things aren't going well though. It looks like we're on our own for this one.
The Field Office
After that's done, drive over to the marked office. Go inside and get the three notes off of the two desks. This includes a demolition order, a memo and a list for a cement purchase. Once you walk out, you'll need to do a very quick fistfight. This should be easy. He'll back off after a few hits and give you free reign on the site.
Walk over to the collapsed home and and check the flags. The important one is the one in the back left. Grab the bottom piece of wood to piece together that the wood is from Keystone Films. You apparently made someone very mad though. We now need to outrun this bulldozer.
Note that you can't kill the driver. Pointing your gun at the driver makes him raise the arm to shield himself though. This means that he can't see, so he drives slower. Jump the first obstacle, then turn around and fire a few shots at him to make him raise the shield.
Run and jump a bit until you hear Kelso start cursing after a few obstacles. Turn around and draw down on the driver to get him to raise the shield again. Repeat this one more time and you should be able to jump past the pipes and climb the ladder. And of course, if you can't beat it, just fail it a few times and enable action scene skipping in the options.
Drive over to the gamewell and call in the address request to get the address of Keystone Films.
Drive over to the new address and approach the gate. You'll automatically talk to the guard and bribe your way in. Just run up to the gate to hop over it. Our goal is the building to the left. Go inside and note the film canister from the Suburban Redevelopment Fund.
Walk over to the trunk and open it up to reveal a projector. Turn the top knob to the right until its in focus, then turn the knob below it to the left until the speech sounds understandable. Flip the switch below it to get the film flowing in the right direction. Then just watch it for your update.
Go back toward the car and jump the other gate to reach the lumber yard. Check the first pile for the receipt, and the second pile for the “inferior quality” tag.
Use the telephone in the security guard's office to call Benson.
Elysian Fields Site Two
Walk up to the house and then note the blinking light inside. Walk inside and then take a look around. You can note the broken light switch and sink, if you want to confirm the theory that these are just for show. Go upstairs to find the blinking light and walk right into an ambush. The fistfight is actually unwinnable, so don't worry about it. Taking out one of the thugs will just mean that they decide to gang up on you and take you out in a cutscene.
When you regain control, run for the car that's stopped at the end of the street. Get in and move toward heavy traffic. There are a few cars tailing you, but they should get caught up in traffic just fine. Take whoever manages to slip past the traffic and push them into a lamp post, another car or just get into their left side and flip them. Once you're in the clear, just drive to Elsa's Apartment to close the case.
All information and screenshots from L.A. Noire
Due to the branching nature of the game, my playthrough may have been different than yours. Please feel free to post any differences that you noticed in the comments below.