Atomfall Complete Walkthrough: Main Story, Best Endings, and Critical Choices

This walkthrough covers the critical path through Atomfall. It's not going to hold your hand through every side activity — there are separate guides for collectibles and secrets. This is about getting through the main story without wasting hours on dead ends.

Act 1: The Village (Hours 1-5)

You wake up in a Protocol bunker. Voice on the radio. Grab the key from the desk (it's literally on the desk, I missed it once), take the pipe from the corpse in the corridor, and follow the tunnel out.

The bunker exit drops you in the Cumbrian countryside. Follow the dirt path south toward the village. Search the farmhouse on your left for early crafting materials — cloth, alcohol, maybe a bandage.

In the village, find the doctor (building with red cross). She's your primary contact for Act 1. The conversation branches based on your dialogue choices — be honest about the bunker and she'll give you more information. She wants you to find a missing medical shipment. This is your first Lead.

Before leaving the village: talk to every NPC, search every building that isn't marked as owned, grab the cricket bat from the shed near the doctor's house, and find the rusty pistol in the shed behind the village. Open your Leads tab and read everything.

The missing shipment is in an overturned truck on the road east of the village, near the Outlaw camp. You'll fight your first human enemies here — three Outlaws. Stealth approach from the treeline, pick off the patrol, then deal with the two by the fire. Search the truck for the medical crate and the Outlaws for supplies.

Return the crate to the doctor. She'll give you more information about the Interchange and reveal the Protocol's interest in the area. This conversation is when the faction lines start to become visible.

Act 2: The Interchange (Hours 5-12)

The doctor directs you to the Interchange, a massive underground complex north of the village. The entrance is a sealed bunker door — the keycard comes from a Protocol patrol you encounter on the road north. Either fight them for it or trade for it if you're friendly with Protocol.

Inside the Interchange, you'll find four wings radiating from a central atrium. The layout: north wing is Protocol territory, east wing is contested, south wing is a neutral trading hub, west wing is rebel-controlled.

Start in the south wing. Meet the traders. Check everyone's inventory. The Protocol quartermaster in the north wing sells the firearms manual. The rebel quartermaster in the west wing has the melee manual accessible on a shelf (not for sale, just pick it up if your rebel rep is neutral or better).

Your main objective in the Interchange is to figure out what happened here. The central story thread involves a scientist who was working on something related to the Windscale disaster. Follow the Leads labeled with his name — they're scattered across multiple wings.

Key story events in the Interchange:

• The Overseer boss fight (central wing, after following three scientist Leads)

• The faction confrontation in the east wing (you'll be asked to pick a side)

• The flooded lower levels (access the scientist's lab)

The faction choice in the east wing is the first major branching point. Rebels want you to sabotage Protocol equipment. Protocol wants you to identify rebel spies. You can delay this choice by exploring other wings first, but eventually you must pick. Your choice locks you out of the opposing faction's vendors.

Act 3: Faction Allegiance (Hours 12-20)

After the Interchange, the game splits based on your faction. I'll outline all three paths.

Rebel Path

You work with the rebels to expose Protocol's cover-up of the Windscale disaster's true severity. Missions involve infiltrating Protocol facilities, stealing documents, and sabotaging equipment. The rebel path has the most stealth-focused missions.

Key missions: steal the Windscale report from the Protocol command center, rescue captured rebels from the military base, and confront the Protocol commander at the comms tower.

The rebel path gives you access to suppressed weapons and scout armor. It's the best path for stealth builds.

Protocol Path

You work with Protocol to maintain order in the quarantine zone. Missions involve hunting rebel cells, securing research data, and suppressing cult activity. The Protocol path has the most combat-heavy missions.

Key missions: eliminate the rebel cell in the village, secure the research lab in the deep quarantine zone, and defend the comms tower from rebel assault.

The Protocol path gives you access to heavy armor and military-grade weapons. Best for combat-focused builds.

Cult Path

Unlocked by rejecting both Protocol and rebels at multiple key moments. The cult leader approaches you in the Interchange after you've angered both major factions. Cult missions are the strangest — they involve ritual sites, mutated creature encounters, and piecing together the cult's apocalyptic beliefs about Windscale.

Key missions: activate the ritual sites around the quarantine zone, survive the trial in the deep cave system, and confront both faction leaders in the final encounter.

The cult path gives you access to unique consumables and the hardest final boss fight. Story-wise it's the most revealing — you learn the actual truth about what happened at Windscale.

Act 4: The Truth About Windscale (Hours 20-25)

Regardless of faction, the final act takes you to the deep quarantine zone. The scientist's research reveals that the Windscale disaster was worse than publicly known — the radiation has been mutating things in ways Protocol has been covering up.

This act is combat-dense. You'll fight through mutated creatures, faction enemies, and environmental hazards. The reactor area is the final dungeon — a multi-level industrial space with radiation zones, flooded sections, and the Beast boss fight.

The exact sequence depends on your faction, but the endpoint is the same: you reach the reactor core and discover the truth. What you do with that truth determines which of the six endings you get.

Act 5: Endings (Hour 25+)

The final choice happens at the reactor core. Your options depend on your faction and earlier choices.

1. Protocol ending: suppress the truth, quarantine continues. Access to Protocol gear and post-game clean-up missions.

2. Rebel ending: expose the truth, quarantine breached. Access to rebel gear and post-game liberation missions.

3. Cult ending: embrace the mutation, quarantine zone transformed. Unique post-game state with different enemy configurations.

4. Independent ending: destroy the research, no faction wins. Requires rejecting all three factions at key moments.

5. Sacrifice ending: stay in the reactor to contain the radiation. Unlocked by specific dialogue choices with the scientist throughout the game.

6. Escape ending: leave the quarantine zone without resolving anything. Simplest to unlock — just leave through the perimeter gate. Least satisfying but technically an ending.

You can save before the reactor core and branch your file to see multiple endings without replaying the full game.

Post-game, the quarantine zone remains explorable with some changed enemy placements based on your ending. Side content and collectibles persist.