Atomfall Captain Grant Sims mission walkthrough

Atomfall offers six different endings, and Captain Grant Sims is one of the six key people who can help you escape the quarantine zone. This is important as in Atomfall, you are trapped inside the zone and must uncover the mysteries behind the Interchange — the secret facility responsible for the disaster — while finding a way to escape.

To fully understand the storyline, you need to interact with Dr. Garrow and Dr. Alan Holder and complete certain objectives. However, if you only want to learn fragments of the story and escape, you can take any of the six available routes.

This article will cover the missions and objectives given by Captain Grant Sims to help you escape with him in Atomfall.

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Captain Grant Sims’s main mission walkthrough in Atomfall

At the start of the game, you will encounter a scientist in a hazmat suit who asks you to investigate the Interchange. He will hand you a modified keycard to access its doors.

Locate Captain Sims

Interact with Captain Sims (Image via Sportskeeda Gaming || Rebellion)

Upon exiting the bunker, you will find yourself in Slatten Dale. Take a left and proceed to two broken structures. Inside the right one, you will meet Nac, who will tell you about a hidden settlement called Wyndham Village and its entrance location. He will also mention Molly, a trader in Slatten Dale.

Head to Wyndham Village, where you will find Captain Grant Sims in the Village Green. Interact with him, and he will ask you to follow him into the Village Hall. Once inside, he will request your help in investigating unusual activities around the village to earn his trust.

Start by heading to the Church, where you will witness a murder. Report back to Captain Sims. Afterward, he will ask you to retrieve information from Dr. Garrow about a strange device called the Signal Redirector. She is held as a high-priority prisoner at Skethermoor Prison.

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Retrieve the Signal Redirector from Skethermoor Prison

Retrive the Signal Redirector in Atomfall (Image via Sportskeeda Gaming || Rebellion)

Since Captain Sims will grant you permission, the guards and Protocol Army inside the prison will not be hostile. Head to the lowest section of the prison to find Dr. Garrow.

• Interact with her to gather information.
• She will reveal that the Signal Redirector is in the Security Room, just north of her cell.
• Collect the device and return to Wyndham Village to report back to Captain Sims in the Village Hall.

Captain Sims will then ask you to retrieve another item: a stolen radio part.

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Retrieve the Protocol Radio Part – The Speaking Cave (Casterfell Woods)

Finding the stolen radio part in Atomfall (Image via Sportskeeda Gaming || Rebellion)

• Travel to Casterfell Woods via the northwestern exit of Wyndham Village (coordinates: 29.6E, 83.6N).
• Once inside, head west to The Speaking Cave (coordinates: 23.0E, 85.4N). Look for a door beneath a hill.
• Inside, you will encounter hostile druids, so proceed carefully and eliminate them.
• Continue forward until you reach a large branched statue. Behind it, on an elevated section, you will find a door leading to an offering room.
• Inside, you will find the Protocol Radio Part. Collect it and return to Captain Sims.

Sims will then assign you the final task: destroying Oberon, the alien meteor responsible for the disaster.

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Activate the Interchange

To enter Oberon, you must first activate the Interchange and open the entrance to the Windscale Plant.

There are four entrances to the Interchange, located in:

• Slatten Dale: 31.0 E, 77.8 N
• Wyndham Village: 33.8 E, 78.3 N
• Skethermoor: 39.6 E, 73.1 N
• Casterfell Woods: 27.6 E, 83.6 N

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Collect at least 4 Atomic Batteries

Before heading inside, collect at least four Atomic Batteries, which are crucial in the game. Here are the best ways to find them:

Atomic Battery in Atomfall (Image via Sportskeeda Gaming || Rebellion)

• Defeat robots – All robots are powered by Atomic Batteries, so destroy them and collect the battery. However, they are formidable enemies.
• Trade with Molly (Slatten Dale) – Trade an Atomic Battery or kill her to loot it.
• Solve the murder mystery at St. Katherine’s Church – Receive a chest key as a reward, which opens a chest containing a battery. You can also kill the Vicar to loot the key.
• Find a broken robot in Skethermoor – Near Nora’s Camp, submerged in water.
• Trade with Nora (Skethermoor) – Trade a battery from her or kill her for it.
• Greenhouse Landmark (Vehicle Storage Bunker) – Find the Storage Room Keycard on a bunk bed and use it to unlock a room with a battery.

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Powering up the Interchange

• Enter the Interchange via the Slatten Dale entrance and go to the Central Processing Center.
• Inside, collect another Atomic Battery and insert it into the console to bootstrap the Interchange.
• Now, power up the four Data Centers: Alpha, Bravo, Charlie, and Delta.
• Entrances and Corresponding Data Centers:
• Slatten Dale Entrance - Power up Charlie and Delta Data Centers.
• Skethermoor Entrance - Power up Alpha Data Center.
• Wyndham Village Entrance - Power up Bravo Data Center.
• Once all Data Centers are online, return to the Central Processing Room.
• Use the Signal Redirector to connect the power lines leading to the processing console.
• After all connections are set, pull the lever to activate the Interchange, granting access to Windscale Plant.

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Destroy Oberon

Activate all four explosives in Atomfall (Image via Sportskeeda Gaming || Rebellion)

• Enter the Windscale Plant. Be cautious, as alien substances will infect you upon exposure. Move quickly through the area.
• You will encounter infected enemies — either eliminate them or run past them.
• Eventually, you will reach a door leading to the Oberon Dig Site.
• Inside, you will find the dig site and a building on the left.

Activating the explosives

• Be wary of hostile robots at the dig site — eliminate them.
• Locate four planted explosives around the dig site. Activate each of them.
• Enter the control room inside the building.
• Pull the self-destruct lever to destroy Oberon.

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Escape to Skethermoor Camp

• After destroying Oberon, return to the Interchange.
• You will receive instructions that Captain Sims is waiting at Skethermoor Camp.
• Head there and find a plane ready for departure.
• Board the plane with Sims to end the game.

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That covers everything there is to know regarding Atomfall Captain Grant Sims's complete mission walkthrough guide.