Replaced: Chapter 4 Walkthrough – Brothers in Arms 100% Guide

Replaced Chapter 4 Walkthrough – How Brothers in Arms Really Flows

After spending an evening combing through Chapter 4 again for 100% completion, I realized most of my early frustration came from missing small side paths and scan prompts in the hospital and station hub. This walkthrough breaks down Brothers in Arms in the exact order I now run it: story-safe, no spoilers beyond this chapter, and efficient for scooping every upgrade, scan, and music track along the way.

Chapter 4 is basically a dense hub episode: you wake up in a hospital, explore the train station, run several optional side quests, then wrap with a council meeting and a short transition to the next chapter. The catch is that some of the best upgrades are very easy to miss if you just follow the main objective marker. I’ll flag everything you should grab before you leave each area so you don’t have to replay it later.

Step 1 – Hospital Flashback: Scans and the Old Man’s Side Quest

The chapter opens with Warren in a hospital built into the train station. This section is calmer than the previous chapters but it hides key upgrades. Don’t rush for the exit; you want to deliberately sweep the area before moving on.

As soon as you gain control, explore the ward and start scanning anything interactable. The game is subtle with scan prompts here, and I missed several on my first run.

• Scan: “Doctor’s Orders” – This is usually close to the starting area, on or near a bedside or wall chart. It sets up hospital context and counts toward your scan total.
• Talk to the patients and staff you can interact with; some of their dialogue changes slightly depending on when you approach them, but the main thing is ensuring you don’t advance too fast.

The most important thing in this section is the old man who’s worried about his family. On my first run I treated him as just another NPC, walked away, and only realized later he was tied to a permanent health upgrade.

The Old Man & Health Increased 5 Upgrade

Find the elderly patient who talks about wanting to see his family again. Interact with him fully to trigger his mini-quest. You’re essentially piecing together clues about his family and their fate, which culminates in a simple but easy-to-miss puzzle.

You will need to check nearby rooms and corridors for additional notes and environmental hints. As you explore, you should come across items tied to his story, including a ring-code style puzzle. The layout is straightforward: several rings or elements you need to align correctly based on the information you’ve just gathered from the hospital notes and the old man’s dialogue.

Once you solve that puzzle and complete his request, you’ll receive:

• Upgrade: Health Increased 5 – A flat boost to maximum health for the rest of the game.
• Scan: “Family Photo” – Adds to your collectible log and fleshes out the background of the station’s residents.

Do not leave the hospital area without resolving this. That health bump is significant on higher difficulties, and backtracking here later is not possible in a clean way.

Outside the Safe Zone – “Nursery Rhyme” Scan

Before following the path that definitively moves you on, look for a chance to briefly step outside the clearly marked safe medical area. There’s a side path that feels a little off the main route, usually toward a more run-down corridor or a less-lit space.

Out there you’ll find the “Nursery Rhyme” scan. It’s one of those flavor pieces that doesn’t change gameplay directly but is vital if you care about full scan completion and atmosphere. I missed this on my first visit because I assumed the “unsafe” section was just environmental dressing.

Once you’ve collected Doctor’s Orders, Family Photo, Nursery Rhyme, and grabbed the health upgrade, you’re safe to push the story forward and leave the hospital flashback behind.

Step 2 – Train Station Hall: Meeting Edward and Tempest

The perspective shifts from the hospital into the wider station hall, which functions as your hub. Think of this area as the core of Chapter 4: most side tasks and upgrades point back toward here one way or another.

You’ll encounter two important characters:

• Tempest – The resistance-linked figure whose room and map become key plot points later in the chapter.
• Edward – A desperate would-be escapee who fixates on Tempest’s map as his chance out of the station.

Edward confronts you and demands Tempest’s map. On my first run I followed the objective marker too quickly and didn’t fully explore the hall. Instead, take a lap around the station, interact with background NPCs, and get a feel for where the arcade, Yo-yo’s lab, and other key doors are. It pays off later when objectives start bouncing you around the hub.

This is also a good time to mentally map the vertical layers of the station. Some collectibles sit on slightly raised walkways or off to the side, and if you always hug the “critical path” you’ll walk right past them. If something looks like a side stair or a dead end, check it once before moving on; Chapter 4 hides several of its scans exactly like that.

Step 3 – Edward’s Death Investigation & Rechargeable Ampoule #2

After the initial confrontation about the map, the story will eventually push you into discovering that Edward has died. This is the point where the chapter shifts from calm exploration into a more investigative tone.

When the game signals that Edward’s body has been found, return to the spot indicated by your objective marker. From here, slow down and treat it like a crime scene: walk around the immediate area and scan every highlighted object before you leave.

• Scan: “Edward’s Diary” – Crucial for understanding his motivations. This is a major lore piece and also part of your scan completion.
• Upgrade: Rechargeable Ampoule #2 – This is easy to miss if you beeline out after seeing the body. Check nearby interactables and containers; look for anything that glows or pings with your scan ability.

On my first clear, I walked away with only the diary, assuming the story beat was done. When I compared my collectibles later, I realized I was missing an ampoule in the chapter and had to replay the whole thing. The lesson: whenever the game shifts to a “big story moment,” assume there is at least one mechanical reward hidden in the aftermath.

Step 4 – Yo-yo’s Lab: Med-Stims 2, Scans, and Excalibur the Cat

Once you’re free to roam again, head to Yo-yo’s lab. This room is your main upgrade hub for utility and healing in Chapter 4, and it also carries some of the denser lore via logs and experiments.

Scans in the Lab

Inside the lab, you should be able to scan at least two notable entries:

• “Solar Panels are Safe” – A technical note about the station’s energy sources.
• “Laboratory Incident Update” – Hints at past experiments and complications.

These aren’t just lore; they contribute to the rough total of a dozen scans you can pick up across Chapter 4. If you’re tracking numbers, this is where most completion runs make sure they’re in sync with a running checklist before moving back to the main hall.

Med-Stims 2 Upgrade

Talk to Yo-yo and interact with the upgrade apparatus to secure Med-Stims 2. This improves your healing capacity and becomes extremely important in the more combat-heavy chapters that follow.

The game doesn’t force you to do this right away, but putting it off is a mistake. On higher difficulties especially, you feel the difference of this upgrade as soon as the next combat section ramps up. I now make it a rule: the moment Chapter 4 lets me into the lab, I don’t leave until Med-Stims 2 is unlocked.

Feeding Excalibur (Cat Quest)

Yo-yo’s lab is also where you interact with Excalibur, the station cat. This side quest is easy to skip if you’re focused only on the main story, but it has some of the best rewards for the chapter.

• Find food for Excalibur and bring it back to complete the feeding step.
• Once done, you’ll be rewarded with:
  • Item: Station Meal
  • Upgrade component: Reduction Gear #1
  • Scan: “Unsent Letter to Mole”
  • Music track: “Prayer of The Damned Ones”

The Reduction Gear component becomes part of your progression toward stronger gear overall, and the music track unlock adds flavor to your in-game jukebox. The main trick here is simply remembering to come back after grabbing the food; the game won’t nag you about it.

Step 5 – The Arcade: Kinetic Inductor 2, “Mommy’s Letter” and Music

Next, make your way to the arcade section of the station. Chapter 4’s arcade is more than a visual setpiece; it hides both gear and story collectibles.

There are three things you want to do here:

• Play the arcade machine – Completing the required game or challenge will reward you with Kinetic Inductor 2, a weapon or ability upgrade that directly helps in future fights.
• Scan: “Mommy’s Letter” – Usually near or around the arcade machines. It’s a poignant note that adds to the station’s backstory.
• Unlock music track: “Great Power, Great Responsibility” – This often ties into a terminal or jukebox-like interaction in the arcade area.

The arcade mini-game can be a minor skill check depending on your reflexes, but it’s absolutely worth the time. On my initial playthrough, I left this until late and regretted not having Kinetic Inductor 2 for earlier encounters. On a replay I prioritized the arcade right after stabilizing the station hall storyline, and the difference in combat flow was noticeable.

Step 6 – Tempest’s Room: Copying the Map and Final Scans

Eventually the plot directs you to Tempest’s room. This is the final major exploration pocket of Chapter 4 before the council meeting and outro, so treat it as a last chance to scoop up scans and lore in this part of the station.

Copying the Map

The main objective here is to copy Tempest’s map. Look to the right side of the room; that’s where the interactable you need is normally placed. Approach it and follow the interaction prompts to create your copy. This is what Edward was so obsessed with earlier, and it’s what feeds into the escape and resistance plans discussed in the following scenes.

Scans in Tempest’s Room

Beyond the map, you can scan additional logs and items. The exact numbering can vary slightly depending on how you’ve collected earlier scans, but you should at least find:

• “Old Logs” – Notes tied to Tempest’s past operations.
• Additional station-related entries such as “Phoenix Initiative Takes Control”, “About Reach”, or “Ironwood’s Note” depending on your route through the chapter.

Total, Chapter 4 houses roughly 12 scans, 2 music tracks, 4 upgrades (health, Med-Stims 2, Kinetic Inductor 2, Reduction Gear component), plus 1 cat quest and 1 genetic profile if you’re chasing 100%. If you’ve followed the steps above, you should be on track to have them all before you leave Tempest’s space.

Step 7 – Council Meeting and Exit to the Garage

Once the map is copied and you’ve finished exploring, the story marches you into the council room. This is mostly a cutscene-heavy section where you get a clearer look at the power dynamics inside the station and the tension surrounding the Phoenix Initiative and Reach.

There are no major mechanical challenges here, but it serves as the narrative payoff for all the exploration work you’ve just done: Edward’s desperation, Tempest’s planning, Yo-yo’s covert experiments, and the civilian lives you’ve glimpsed all come together in the discussion.

After the council sequence concludes, follow Tempest to the garage. This is a mostly linear walk, and as far as current guides and playthroughs show, there aren’t additional hidden scans here. Once you reach the car and the final short cutscenes play, Chapter 4 transitions seamlessly into the next chapter.

Practical Wrap-Up – What to Double-Check Before Leaving Chapter 4

Before you mentally close the book on Brothers in Arms, it’s worth mentally ticking through a quick checklist. This is how I confirm a clean Chapter 4 when I’m going for a 100% save:

• Hospital: Doctor’s Orders, Nursery Rhyme, Family Photo scan, Health Increased 5 from the old man’s side quest.
• Edward storyline: You inspected his death scene fully and picked up both Edward’s Diary and Rechargeable Ampoule #2.
• Yo-yo’s lab: Solar Panels are Safe and Laboratory Incident Update scanned, Med-Stims 2 unlocked, Excalibur fed and its associated rewards collected.
• Arcade: Kinetic Inductor 2 from the arcade machine, Mommy’s Letter scan, Great Power, Great Responsibility music track unlocked.
• Tempest’s room: Map successfully copied, Old Logs and other available scans picked up.
• Council & Garage: No collectibles missed (this section is essentially narrative only).

Run through that list before you follow Tempest to the garage and you’ll leave Chapter 4 in excellent shape for the rest of the game. The upgrades you secure here – especially Health Increased 5, Med-Stims 2, and Kinetic Inductor 2 – meaningfully smooth out the difficulty curve in later chapters, and the scans and music tracks give you the full picture of what’s really happening inside the station.

If you treat Brothers in Arms as a chance to catch your breath, explore thoroughly, and tune up your build, the chapters that follow feel less like a difficulty spike and more like a natural escalation. Take the time to squeeze everything out of this hub while you’re here; the game is designed to reward players who slow down in Chapter 4 and pay attention.