Before players can create serum in Resident Evil 7, they need to find the D-Series Arm and D-Series Head. While Zoe claims to have the D-Series Head, Lucas Baker – one of Resident Evil 7’s main antagonists – intercepts it while Ethan is hunting down the D-Series Arm in the main house. Only after finding both keycards inside the Baker Main House can players finally start tracking down the D-Series Head to make serum.

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Like most things in Resident Evil 7, though, this is no easy task. The path towards making serum forces Ethan to confront Lucas’ deadliest traps and one of Resident Evil 7’s hardest boss fights: Mutated Jack. Just getting to Jack is a trial in and of itself, throwing Ethan into the very same “Happy Birthday” gauntlet that ultimately took Clancy’s life.

Ethan’s path to serum and Jack also has him running into Fat Molded for the first time: the single most dangerous type of Molded in the game and an ammunition guzzler if there’s ever been one in Resident Evil. Leading into the last stretch of the game, making serum and defeating Mutated Jack is one of Resident Evil 7’s hardest challenges.

Battle Of The Barn

Fat Molded

After failing to input Lucas’ password (actually a scripted sequence) and dodging his subsequent death trap, Ethan will be able to make his way down into the Baker Barn. Make sure to bring along the Burner to comfortably disarm tripwire and trap crates from afar. The flamethrower can also be used to quick-stun the Molded up ahead.

Be prepared to take on some Quick and regular Molded on the way to the Barn elevator. Go slow and try to avoid damage by guarding. Shotgun blasts to the face will take out most regular Molded if at close range, and a few Handgun bullets to the head comfortably drop Quick Molded (make sure to shoot them from afar).

Stay perceptive of tripwire as you enter into the elevator room and grab the Battery up the staircase. Once the elevator has been powered on with the Battery, Ethan will come face to face with his first Fat Molded. Always run away & keep a distance when its puking and Shotgun blast it in the face whenever there’s an opening. Once the Fat Molded has been killed, take the elevator to enter a new room where a note reveals the real password: 1408.

Lucas’ Game

RE7 Loser

Even though Ethan now has the password, Lucas won’t actually let him past the door unless your inventory is completely empty. Unload everything and head inside to realize Ethan now has to solve the Happy Birthday puzzle that took Clancy’s life. If you haven’t already watched the Happy Birthday tape, reload and do so ASAP – it’s the only way to survive Lucas’ game.

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Grab the Candle from the clown and head into the cake room, but do not rip the Winding Key out of the cask. Turn on the stove top and light the Candle to burn the rope that leads into the balloon room. Input “LOSER” into the 5-character lock and grab the valve off the wall. Install the valve in the cake room, turn off the sprinkler, light the Candle, and place it on the cake.

The cake will explode, but it won’t hurt Ethan or set the room on fire. Lucas will quickly toss a stick of dynamite into the room. Rush over and pick it up. Examine the wall to rip off the paneling and toss the dynamite in. Its explosion will open a path into Lucas’ room where you’ll be able to finally grab the D-Series Head.

Rescuing Mia & Zoe

Zoe with D-Series Arm and Head

Now that Lucas has been beat at his own game, it’s time to rescue Mia and Zoe. Check the monitor on Lucas’ desk and grab the Handgun, Shotgun, Burner, Crank, and some First Aid Med out of the Item Box. Ethan will be coming up against quite a few Molded on the way to the Boathouse.

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The path will be clear at first, but Molded will start spawning once Ethan reaches the Crank panel. Lower the bridge, turn around, and get ready to fight. There are three regular Molded and two Quick Molded in the area, so take them all out carefully. Try not to waste too much ammo, though, since Mutated Jack still has to be dealt with.

Once all the Molded have been killed and you’ve crossed the bridge into the Boathouse, grab the D-Series Arm and D-Series Head out of the Item Box along with all your ammo and at least 2 more First Aid Meds. Head into the Boathouse to find Mia and Zoe tied up. Free them both, give Zoe the D-Series Arm & Head and get ready to fight Jack one last time.

Mutated Jack Fight

RESIDENT EVIL 7 biohazard Mutated Jack

Mutated Jack is an extremely aggressive boss with a large arena spread across two floors. Make sure to loot the arena before anything else since the battle will become far too hectic later to scavenge. The goal here is to pop all eight of Jack’s eyeballs while blocking and dodging his attacks. His eyeballs are located on:

  • His face.
  • His belly.
  • His right torso.
  • His right arm.
  • His left arm.
  • His tail.
  • Under his tail.
  • His back.

The fight will end when all eight eyeballs have been popped, giving Ethan the chance to inject Jack with serum – putting an end to him on the spot. The Burner is actually fairly useful in this fight and capable of dealing damage to the harder to reach eyeballs. It’s best to save it for closer to the end of the face, though.

Take out Jack’s face with the Shotgun whenever he comes to the top floor and shoot him with the Handgun from up above when he’s down below. Make sure to guard anytime Jack is about to do damage and be patient when trying to hit his eyeballs. Precise shots are better than plenty of shots. With Jack dead, Ethan now has to choose between saving Mia or Zoe with the last remaining serum.

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