Soul of a Heretic

Gedō no Tamashī (外道の魂) is the 1st chapter of the 15th volume and the 59th chapter overall of the Attack on Titan manga, written and illustrated by Hajime Isayama.

Overview
Nile Dok ponders over whether the Military Police First Interior Squad will use the new Anti-Personnel Vertical Maneuvering Equipment against regular Military Police members while the press attempt to get answers. Armin comes to terms with committing his first crime, murdering the soldier that nearly shot Jean, although Mikasa, Levi and Jean encourage and thank him. Later, two soldiers, Hitch Dreyse and Marlowe Sand, are caught when they stray from their patrol group and are detained by Squad Levi. Hitch learns about what happened to Annie after the battle of Stohess District, while Marlowe pleads to help Levi. When Jean is given custody of the captured pair and told to release them, he tests Marlowe's honesty by having a brief fight, and Hitch tries to intervene. They both agree to aid the Survey Corps. Using Marlowe's intel, the group locates the Interior Brigade Compound, where they suspect Eren and Historia are being kept.

Summary
In the aftermath of the battle between the Survey Corps and the First Interior Squad in Stohess District, Commander Nile speaks with the chief editor a popular newspaper. Peaure, the man's assistant, notes that the First Interior Squad is a separate branch from the regular Military Police, but is stopped by the editor, who apologizes to Nile for Peaure's inexperience and tells him that the newspaper won't report anything on the First Interior Squad. Nile requests him to not report anything on the Anti-Personnel Vertical Maneuvering Equipment either. He then proceeds to leave, wondering if the First Interior Squad will one day use such equipment against him as well.

Elsewhere, a traumatized and crying Armin kneels beside a tree, vomiting on the grass. Mikasa comes out of the stable and hurriedly goes over to comfort him; Armin asks Mikasa if she had experienced such psychological trauma as well, but then starts apologizing to her. Mikasa heads back into the stable, where Levi is getting stitches from Sasha on the shoulder wound he received from the First Interior Squad's attack. She goes over to Jean and tells him that it's his turn for guard duty, offering her rifle. Armin had saved Jean's life by shooting one of the Military Policeman on the carriage in Stohess.

A few hours later, Squad Levi sits together, eating food beside a fire. Levi notices Armin's discomfort and asks him if he can't stand eating in a filthy stable, which he denies. Armin recalls that he was the one to take the first shot despite Jean's attacker having drawn and point her gun first. The attacker's hesitation to kill Jean saved his life. Levi comforts Armin by explaining that had Armin not fired, Jean would not have survived the operation.

The next day, Hitch Dreyse, being ordered to accompany Marlowe Sand in an attempt to capture wanted Survey Corps members, patrols deep in a forest alongside him. Hitch expresses her opinions on the recent events that happened in the Stohess District, and questions where Annie is, also telling Marlowe that she was her roommate when Annie served in the Military Police. Their conversation gets interrupted when Hitch hears the sound of water and silences Marlowe, asking him to get his gun ready. The two see Armin Arlert getting water from the nearby river.

Hitch and Marlowe both order Armin to put his hands up into the air, only to fall into his trap. Mikasa and Levi then jump behind the two. They then proceed to take their guns away from them and rid of their other weapons and uniforms. Levi questions Hitch and Marlowe about their current positions in the Military Police. Hitch, angry at the Survey Corps, blames Levi and the entire military branch for the aftermath of Stohess and of Annie's apparent death. Hitch and Marlowe soon learn that Annie was the Female Titan that was in Stohess and she is captured and still alive. Marlowe tells Levi that he would like to help the Survey Corps, but Levi doesn't buy in and orders Sasha to escort them someplace else. Jean interferes and offers to take the two instead. Taking Marlowe and Hitch to the area, Jean threatens them with a knife along the way.

Arriving at the spot where Jean wanted them to be at, Jean admits he intends to kill the two of them with the knife he had believing them to be a threat and cannot be trusted. As Marlowe explains that Levi didn't want Jean to kill them, Jean says that this was his own personal decision, and that none of the other members know about it. Jean raises the knife in the air as the two beg for their lives to be spared about to stab them to death, but Jean trips and the knife falls from his hands. Marlowe grabs the knife and tells Hitch to run. Jean and Marlowe are soon struggling for the knife when Jean gets back up on his feet. Jean tells Marlowe that he also has a gun that can hurt them, and that it would be of more use as it shoots faster than how a knife can stab. Marlowe confesses that he really was on their side, and his personal view of the Military Police Brigade. They both stop struggling when Hitch grabs a nearby stick and rams it into Jean's head, sending him to the ground. Hitch attempts to hit him again with the stick, but is stopped by Marlowe. Marlowe tells Hitch that Jean was only testing him, and he never was serious on killing them after all. Marlowe questions Jean about why he trusts him so much, and Jean responds by saying that Marlowe reminds him of someone he hated, which Marlowe suspects to be the same person Annie spoke of. Marlowe reaches his hand out to help Jean up, and Jean confirms that Marlowe and Hitch can be trusted and their strength could be of use.

Hitch and Marlowe lead Mikasa, Connie, Sasha, Levi, and Jean to the Interior Brigade Compound, where they are ready with rifles. Levi says that it was thanks to Hitch, Marlowe, and Jean that they made it this far. They all continue their way to the Compound, saying it is their time to strike.