There’s more than one way to solve the Typhon threat on the Talos 1 station in Prey [2017]. Sometimes the simple solution is best — just kill every human you can find.

Killing every human unlocks the “I And It” achievement / trophy, and will alter your ending. This path even unlocks special quests late in the game, giving you a few more tasks to complete before the story’s conclusion.

If you’re looking to try everything else, check out everything you need to know about unlocking the worst ending below.

More Prey guides on The Escapist:

• Prey: Collectibles, Upgrades & Items Guide | Neuromod Division
• Prey: Collectibles, Upgrades & Items Guide | Talos 1 Lobby
• Prey: Collectibles, Upgrades & Items Guide | Hardware Labs
• Prey: Collectibles, Upgrades & Items Guide | Psychotronics
• Prey: Collectibles, Upgrades & Items Guide | G.U.T.S.
• Prey: How To Get The Best Ending | ‘I And Thou’ Guide
• Prey: How To Get Rid Of Nightmares | ‘You Rang?’ Guide
• Prey: All Weapons Locations Guide | Full Arsenal
• Prey: Fabrication Plan Locations | Crafting Guide
• Prey: Weapon Upgrade Kits Guide | All Locations
• Prey: Keycard Locations & Keycodes List | How to Unlock Every Door
• Prey: How to Dupe Materials | Infinite Materials Guide
• Prey: How To Craft Unlimited Neuromods | Infinite Glitch Guide
• Prey: How To Get The Golden Gun | Unique Pistol Location
• Prey: How to Solve Calvino’s Puzzle | ‘Coffee Break’ Guide
• Prey: Die in 5 Minutes Or Less | “No Show” Easter Egg
• Prey: All 6 Starbender Books | ‘Prism Master’ Guide
• Prey: Complete Trophies List

How To Kill Every Human | ‘I And It’ Guide

Before we begin, there are a few tips you’ll need to know. Killing all humans isn’t as easy as it sounds. Making sure all the humans are dead isn’t enough. You need to be the one that kills them, so accidental deaths won’t add to your tally.

• 1. When encountering mind-controlled humans, you must get the killing blow. Don’t let their heads explore, or let them die due to Typhon attacks. You need to kill them.
• 2. The Security Station terminals and Stats menu will help here. Use the Security Station terminals or other workstations to track living employees. The Stats menu will show you how many humans you’ve killed so far. Check it to make sure your kills properly register.
• 3. Get as many kills as you can before Dahl arrives. If you’ve been killing lots of humans, you’ll get the optional “Showing Initiative” quest. Here, you’ll be able to kill 4 humans that don’t appear on the station otherwise, and they can be missed.

With those notes out of the way, let’s talk about how to kill every optional human you encounter as you progress through the story.

How to Kill Every Human | Complete List

Trevor J. Young (Mind-Controlled): Talos 1 Lobby – Find this mind-controlled human in the Quarantine Cell in the Trauma Center. Get the Trauma Center key from the Transtar desk opposite the Shuttle Bay, then get the Quarantine Cell keycode from Matthias Kohl’s workstation in the Trauma Center.

Aaron Ingram: Psychotronics – Encounter the “volunteer” in the Materials Extraction area of Psychotronics. Use the workstation terminal and release a mimic instead of opening the doors.

Rodney S. Poole + Roni Chaudhary + Mickey Pitt Sr. (Mind-Controlled): Arboretum – There are three mind-controlled humans in the Green House.

Frank Jones + Emmanuella DeSilva: Shuttle Bay – Find the Escape Pod Bay on the lower level, then access the workstation behind the maintenance hatch. Use it to blast the escape pod instead of releasing the locks.

19 Employees (Mind-Controlled): Crew Quarters – The Crew Quarters is full of mind-controlled humans. Use the front desk terminal to track all 19 in the area. Get the Gym keycode from the same terminal’s emails. The full list includes:

• Franz Klinger, Bernard Griffith, Caleb Hawthorne, Carlos Popinga, Daniel London, David Branch, Emma Beatty, Gary Snow, Ike Stewart, Harvey Clausen, Indigo Lake, Jillian Quig, Lisa Larson, Mary Malinaro, Oliver Benoit, Phong Vu, Salman Kapoor, and Vincent Schubel.

Will Mitchell: Crew Quarters – The insidious Cook, kill him immediately after gaining entrance into the kitchen.

Dayo Igwe: Talos 1 Exterior – ‘This Side Up’ quest – Dr. Igwe will request help while you explore the Cargo Bay hull breach. Enter his cargo container number in the workstation in the breach to kill him.

Sarah Elazar + 7 Employees: Cargo Bay – ‘Shipping and Receiving’ quest – The Cargo Bay has 8 humans holed up inside. You can’t let them be killed by the Typhon — you have you kill them all yourself. Kill them all before opening the doors to Cargo Bay B.

• Ekaterina Mulsaev, Tamiko Hayashi, Sam Hertz, Darcy Maddox, Austin Cool, Kevin Hague, and Alfred Rose.

Mikhaila Ilyushin: Power Plant – ‘Reboot’ quest – After rebooting the Power Plant, you’ll get a timed quest to help Mikhaila Ilyushin. Enter her office and shoot her instead of helping.

4 Employees: Life Support – ‘Showing Initiative’ quest – If you’ve been killing humans since the start, Dahl will give you this quest when he arrives late in the story. All four employees are located in Life Support. Quest waypoints will show you where to find them.

• Steve Folson, Harley Grainger, Richard Coveney, and Maxine Ford.

Walther Dahl: Shuttle Bay – ‘Showing Initiative’ quest – After completing the quest, you can meet Walther Dahl in the Shuttle Bay. Break into Flight Control and kill him.

Alex Yu: Arboretum – ‘Keys to the Kingdom’ quest – Alex Yu won’t appear until late in the story. When he agrees to meet with you in his office, open the hidden safe room door and start shooting.

That’s all 42 humans you’ll need to kill to unlock the worst possible ending in Prey. Make sure to stay until after the credits to see the full ending!