Killer is Dead The Carrier of Love is relatively a short mission that takes place on a haunted train, formerly known as Tommy.
Tommy was sent to the museum after it fulfilled its duties during the 20th century. Revived by an unknown entity, Tommy turned into TM-551 and now the train is heading towards Moscow, to destroy those who wish to put it away.
While playing Killer is Dead Episode 10 you can find Scarlett four times, the tenth episode being the final one to feature hidden collectibles.
At the end of the mission, after you defeat Tommy, you will unlock the Scarlett-Approved Stalker trophy/achievement.
Scarletts locations in Episode 10 are covered by the walkthrough below.
Client: Russian Ministry of Defense
When the mission begins, Bryan sends you on the train, while he remains behind. Take out the first Wires that attack you, and then enter the next wagon through the large doors in front of you.
Scarletts Location 17:
Inside the next cart, you should see several capsules occupied by Wires. On the left side of the same room, there are three beds, the one in the middle being occupied by a Wire.
Go behind the third bed and look for a green panel. Activate it to discover Scarletts first location and to unlock Weapon Challenge Part 1.
Now, place Mondo in front of the next door and look up, and to the left. Notice the panel that can be destroyed, and shoot it. Do the same with the panel on the right side, and the door will open in front of you. When you enter the next train cart, you can see that it serves as a supply wagon, which is filled with boxes.
Take out all Wires that ambush you, and observe that some of them spawn on the platform above.
Scarletts Location 18:
Advance killing all Wires that stand in front of you, and when you reach the other side of the wagon, turn right and go around the large containers to find a ramp that allows you to reach the upper platform.
Destroy the box at the end of the platform to find Scarletts second location and unlock Survival Challenge Part 4. Next, retrace your steps, and move towards the next wagon.
Fight the first wave of enemies and eventually you will trigger a cutscene showing Bryan who comes to assist you. Mount Bryans turret and kill the Wires in front of you, then shoot the spheres on the right side of your wagon. After Bryan leaves, use the remaining turret to clear the area of enemies and spheres.
Scarletts Location 19:
On the same cart where you have been helped by Bryan, move slowly towards the other side, keeping an eye on the right side of the wagon, where you should see a pile of crates.
Climb the ladder near the pile and on top of the last crate is another wooden box. Destroy it and inside you will find Scarlett. Talk to her to unlock Trick Challenge Part 4. Descend the ladder, and in the next room (red) shoot the power consoles to open a door on the left side. Climb the next ladder, and you will be on top of the train surrounded by wooden boxes.
Scarletts Location 20:
While trying to avoid the obstacles inside the tunnel, try to destroy all wooden crates, because on the right side of the area, inside one of them is Scarlett. At this point all you have to do is to move forward and dodge when you see the obstacles coming towards you.
When you find Scarlett, you will also unlock the final challenge in Killer is Dead, which is Target Challenge Part 7.
Move forward until you reach the end of the wagon, and you will trigger a cutscene showing Bryan being smashed by the train. After the cutscene you will start the final boss fight.
TM-551 Boss Fight
To defeat TM-551, first you have to cut down the bosss eyes. Start by shooting each eye until you empty their health bar.
As you can see, even if the health bar is empty, the eyes continue to attack you. Make sure that when one of the eyes floats above your head, you shoot it, in order to activate the marker above, then dodge the eyes attack and quickly turn around to cut it down using your finishing move (RT+X).
If you run out of blood and you cant shoot the tentacles while in the air, hit them with your sword when they land on the ground.
During the last phase, you can use the same strategy, but you have to avoid the purple stars fired by the large head. When you cut the final tentacle, you will defeat Tommy, and you will unlock Episode 11, two sub-missions (Pain on the Train and Mans Little Passion), as well as The Skinny Controller achievement/trophy.