Resident Evil 2/Scenario A: Sewers

Left half of the Blue Stone
After extinguishing the fire that once engulfed the helicopter wreckage, with both Red Jewels and the right half of the Blue Stone in your inventory, head back to the hallway where the front end of the helicopter crashed through the wall. You will be surprised to discover that the water we just dumped on the outer part of the copter has also extinguished the flames that blocked you from passing. Ignore the heavily damaged door on the left for now as we will come back to it in a moment. Enter the door just ahead of you on the right. You are now in the Art Room. On either side of the giant knight statue you will notice a carving of a bust with a slot to hold something on their chests. Use your Red Jewels on them and a cutscene with play depicting the giant knight statue's chest armor open up to contain the left half of the Blue Stone. Go ahead and combine the two halves of the Stone and make your way back to the wreckage in the hall.

''If you have not already found the Serpent and Eagle Stones, you can find them in the following locations: Serpent Stone is located behind a painting of what I believe to be Perseus holding Medusa's decapitated head in the library after solving the bookshelf puzzle. The painting resides underneath the broken section of the wooden walkway after ascending the stairs on the wall. The clue for solving the puzzle resides here as well. Eagle Stone is located in Interrogation Room A on the metal shelf opposite the entrance door. This door is unlocked with the Precinct Key with the Heart atop it. Be warned though, a Licker will suddenly burst through the glass from the Observation Room as soon as you turn to leave. Whether you choose to fight it or simply make a mad dash for the door, we will continue where we left off.''

The Plastic Explosive & Detonator
These two items, combined into one prior to use, are required to clear the wreckage in the hallway. The Plastic Explosive is found in the Evidence Room in a large drawer (just one of the wall of drawers) labeled "Explosive". The Detonator is found in the West Office after defeating the now undead officer who locked you out of that section of the PD in the beginning. It's on the desk.

"I used to love taxidermy"
As mentioned, combine the Plastic Explosive and Detonator to yield the Bomb & Detonator and use it at the highly damaged door created by the helicopter. A cutscene will play showing Claire running around the corner and an explosion occurring off-screen. Proceeding down this now accessible hallway you will find the entrance to Chief Brian Irons' office. After taking a few steps forward, you discover a blonde woman laid on the desk, with blood at her abdomen and a large swivel chair turned with its back to you. Interacting here will trigger a cutscene, in brief, showing Chief Irons spinning around with a gun pointed right at you. He realizes you're not a zombie and notes that the most effective way to handle a zombie is to either shoot them in the head or decapitate them entirely. He'll then ask to be left alone, at which point you can now use the door that lies on the other side of the bookshelf from where you came in.

Finding Sherry
Entering this door greets you with the taxidermied body of a tiger with the description: "A stuffed animal". Quite the pun, am I right? Follow this hallway down and enter the next door. Upon closing it, a short cutscene plays but you only hear the sound of feet running away. Walk around either side of the big display case in the center to find the threshold to a little side room. On the wall is a switch, press it. Once you change camera angles by walking a few steps to the right, another cutscene starts, this time depicting a conversation between Claire and Sherry, as well as Claire radioing Leon to inform him of having found Sherry. Following this, Sherry tells Claire about how her parents said that it was too dangerous to stay home and to go to the RCPD, as it was believed to be a safer place for her. She explains that both of her parents work at the chemical factory and then she tells Claire about a big monster that she thinks is after her. You then hear the screams of, what turns out to be, Chief Irons. Sherry, convinced the scream was the product of the big monster finding Chief Irons in its pursuit of her, hesitatingly separates from Claire in search of a safer place. Go back to the office where you will find both Chief Irons and the girl have disappeared.

Chief's Diary
Lying in the Chief's chair is his diary where we discover that the girl is actually the Mayor's daughter, whose safety was entrusted to the Chief by her father, the Mayor of Raccoon City. He goes on to explain his shocking involvement in the Raccoon City Incident by closing off all exits from the precinct and intentionally letting the Mayor's daughter escape, in which he then hunted her down. He also mentions other survivors and hunting them down as well. He then sadistically recounts shooting "Ed" in the back through the heart and watching him writhe in pain on the floor in a pool of his own blood, ending eerily with how beautiful and exquisite Ed's dead, wide-eyed expression staring back up at him was.

Mail to the Chief & descent to Level B-1
Examine the painting on the wall with the indentions for three square objects. Use the Blue, Eagle and Serpent Stones here to show a button that once pressed, reveals a secret door at the left end of the wall. Inside is a file entry recounting three correspondence events from William Birkin to Chief Irons, further solidifying the Chief's involvement in the Incident. From renegade operative Albert Wesker to bribery and threats of poaching his research, Birkin expresses fear-fueled agitation with the situation at hand. After reading these letters, you see a caged elevator that is described as looking like it goes down. The first interaction does nothing but inform you of this. The second interaction, possibly only triggered by exiting the office and re-entering it, shows a cutscene of Claire telling Sherry that she's going down there and to stay here waiting for her return. Sherry agrees and wishes you good luck, at which point the animation of the gate opening, the elevator descending and the gate opening once more to indicate your exiting it, plays. You are now in the hallway directly above the Weapon Storage Room on Level B-1.