Arc 3 of Re:Zero Life in a Different World from Zero also known as Return to the Capital City or The Truth of Zero (for the manga) is the third arc in the series which covers the beginning of the Royal Selection and the subsequent attack by the Witch Cult. It is covered in Volumes 4-9 of the light novel series, spans from episodes 12 to 25 of the anime, and volumes 7-17 of the manga (collectively known as Daisanshou).

Previous: Arc 2 - The Tumultuous Week
Next: Arc 4 - The Everlasting Contract

Synopsis

In The Capital Once More

Emilia is summoned back to the capital city of Lugnica. Subaru tags along to obtain the aid of a healer after damaging his gate in the events of Arc 2. He is convinced that Emilia will need his help and barges into the Royal Selection ceremony. He oversteps his station, embarasses her, and insults the knights of the kingdom. He gets himself hurt and after an argument with Emilia over his actions and intentions, the two part ways with Subaru staying in the capital to heal and Emilia returning to the Mathers mansion.
During this time Subaru stays with Crusch in order to be healed by Felix who is the best healer in the country. He is attended to by Rem who seems to have grown attached to Subaru after the events in Arc 2. One day she gets a bad feeling through her link with her sister and they travel together back to the Mathers mansion. Fearing for the worst Rem leaves him behind to travel ahead. By the time her catches up to her, he discovers that the mansion has been attacked by the Witch Cult and everyone in the village has been killed including Ram and Rem. Subaru dies when he ventures too far into a secret passageway that is completely frozen over.

The Weight of Death

Subaru comes back to himself in the capital once more. The shock of all that he had seen overwhelmed him when he saw Rem alive. He completely shut down emotionally and became completely despondent. He barely reacts to anything and even Felix is unable to help him. Eventually Rem decides to take him back to the Mathers estate in the hopes that seeing Emilia would lift his spirits. This time around they arrive at the Mathers territory earlier than before but the Witch Cult is already entrenched in the forests around Irlam village and the mansion.
In his useless state Subaru gets kidnapped. Rem does her best to fight off the Witch Cult but easily falls when she comes face to face with Petelgeuse Romanee-Conti. The two are left to die alone. Rem manages to free Subaru with the last of her strength and urges him to live with her dying breath. He somewhat snaps out of his stupor and makes it to the mansion but he is once more too late. He dies as Puck unleashes all of his power and freezes the entire area.

Cycles of Death

This time upon returning Subaru is able to keep his wits about him. Over the next few deaths Subaru tries to amass help to save the residents of the Mathers territory, but his efforts always end in failure. The other Royal Candidates who hold the most power refuse to help him as they see no benefit to aiding a competitor for the throne. His attempts at rushing back with wagons and carts to evacuate are met with the terrible White Whale.

What If

The constant failure eventually breaks down his spirit once more. He entertains the notion of running away from all of the problems with Rem. She says that she would love to and fantasizes about a complete and fulfilling life together but eventually says that she believes Subaru will rise to the occassion like the hero she believes him to be.

Whaling

With newfound resolve he once more courts the aid of Crusch and Anastasia. He offers them some resources but most importantly the location of the White Whale at a predetermined time. In exchange he asks for them to help him fight off the Witch Cult after they kill the Demon Beast. The disparate camps decide forge a temporary alliance and prepare an ambush for the ancient beast. Together they are barely able to slay the mighty creature. The combined party is hurt pretty badly in the hunt and only a small group goes on with Subaru to the Mathers territory. Rem and Crusch both retreat to the capital to lick their wounds along with the injured and dead.

The Sin Archbishop of Sloth

With his considerably smaller force Subaru forges on ahead to stop the Witch Cult's plan. With the forces at his disposal Subaru is able to kill Petelgeuse in a surprise attack but they are then besieged by Witch Cult lieutenants known as the Ten Fingers. Petelgeuse is able to possess a new Finger every time his body is destroyed. Subaru and his crew fail to evacuate the villagers before the attack, but through the combined might of everyone present including Emilia who fought on the frontlines all of the Ten Fingers are put down. As they begin to celebrate their victory Subaru gets possessed by Petelgeuse. He manages to retain enough control to beg Julius and Felix to kill him.
He comes to consciousness and discovers that his 'save point' has been updated. He now returns to just after the defeat of the White Whale. Armed with his new knowledge they attack the Witch Cult once more. This time they sneak in and get the villagers and Emilia to evacuate first. Then, they systematically hunt down the Ten Fingers first and leave Petelgeuse for the last. Julius and Subaru face down Petelgeuse alone and are able to destroy his body. When Petelgeuse attempts to possess Subaru, he calls out to Satella by trying to mention his Return by Death ability. The Witch Power within him ejects Petelgeuse's control leaving Subaru safe this time around.

Casualties

The day is not yet fully won however. Emilia and the children she is travelling with are in danger from a sack of fire element magic stones that were stowed in her wagon. Subaru races off to rescue her and finds that the entire evacuating caravan is under attack by another sect of the Witch Cult. The Witch Cult is eventually defeated by the armed escort and Subaru is able to toss the sack of magic stones into the corpse of the White Whale. All seems well until they return to the capital. Rem and Crusch ran afoul of another Sin Archbishop on their trip back. Ley Batenkaitos ate Rem's identity and memories (placing her in stasis) and Crusch's memories using his Authority of Gluttony.

Links

Fan Wiki
MyAnimeList
List of Re:Zero Anime Episodes
List of Re:Zero Volumes