As explained by Marcus Hearn in DWM 567, the story was put together to make up for the lack of the magazine's regular comic strip, which was still on a hiatus at the time due to the COVID-19 pandemic.
Part One: The First Gun
Yasmin Khan faces up to a young man with a gun while on the job as a police officer in a dark alleyway in Sheffield. As Bonfire Night celebrations go on over their heads, Yaz briefly distracts him by describing herself as a time traveller, but he stands firm, aiming the gun at her. She panics internally and tries to remember what she has learnt from the Thirteenth Doctor, thinking back to a previous adventure.
Having visited 5 November 1605, the day of the Gunpowder Plot, to give Yaz a treat to make up for her working on Bonfire Night, the Doctor and Yaz stand over the destroyed ruins of the Houses of Parliament. The Doctor sonics the ashes, knowing that James I has been killed as well and considers who could have interfered with a fixed point in time. She theorises that it may not have been Guy Fawkes. To find out the answers, they travel back to the night before in the TARDIS.
In the undercroft of the House of Lords, the Doctor reminds Yaz to only step in and stop Guy at the last second so history can continue its rightful course. They hide as they spot Guy preparing to commit the crime, followed closely by several men who capture him and lead him away, leading the Doctor and Yaz to wonder if either they witnessed a different man or history had reverted to normal. They are forced to wait the rest of the night to ensure it and eventually spot what appears to be Guy reappearing, shooting two guards and lighting a fuse. The Doctor simply blows it out, at which point she realises that the man is not Guy Fawkes but is wearing a mask of his face. She asks who he is and what he is trying to achieve, but he just states that "the world is growing too fast".
As the man goes to shoot the Doctor, Yaz tackles him, and they crash into a barrel of gunpowder. The fall breaks his mask, revealing a face covered in old bullet wounds. He lights another fuse anyway, but his hand quickly catches fire. The Doctor desperately pulls Yaz into the TARDIS to prevent her from being caught in the explosion, knowing that they have failed in changing history back. Yaz assumes that he must not be human to have taken so many bullets and survive, but the Doctor confirms he is "mostly human" and decides to go back in time, "to his first life".
Landing in Germany a couple of centuries earlier, the Doctor learns that the man was Berthold Schwarz; Yaz's contemporary search reveals him to be an alchemist, friar, and inventor of the gun, but the Doctor begs to differ. She explains how guns have appeared independently in most galaxies, even on Earth, so he must have been looking for something else. Entering the dungeons, the Doctor explains that religious people were often imprisoned for discovering the combination of "gold, God and guns".
They are interrupted by another bang causing a bright white light inside a cell. Breaking in, they discover a young and unscarred Schwarz looking into a portal, with a tall alien figure clad entirely in golden armour, a Varkladian Knight, on the other side. The Doctor realises that the portal had been accidentally summoned through an alchemy experiment and tries to get Schwarz to see sense, but he ignores her and reaches out for the Knight's golden gun. He shoots the Knight, causing him to bleed and scream with pain, and the Doctor begs Schwarz to throw the gun back into the portal before it closes. Yaz tackles him again, but she witnesses a flash, and her vision goes black.
Part Two: The Last Gun
Yaz reawakens inside the TARDIS with hospital monitors tracking her. The Doctor informs her that she was shot but the bullet went straight through her, with her wound having since been fixed, leaving a glowing scar behind. She continues that the TARDIS' translation circuit tried to translate the Knight's scream because it was not the sound of it dying, discovering that it let out a blood curse on Schwarz, making him immortal unless he is shot by the last gun on Earth. The Doctor realises that he planned to blow up Parliament so the resulting war could wipe out every other gun on the planet and secure his peace. Although Yaz attempts to suggest returning to stop Schwarz in 1605 again, the Doctor instead decides to visit his future.
Arriving on far future Earth among endless ruins, the Doctor explains how human civilisation has been destroyed by efficient computer codes controlling bombs that Schwarz launched. The duo eventually spots Schwarz, now an ancient husk ruined by bomb explosions, standing near a pyre of weaponry and the people who made them. He aims a shotgun at his head, but Yaz distracts him by showing him her scar. Distracted, they try to talk him out of his plan by proving how Yaz is unwilling to use his gun and suggest that he can have faith in humanity and save people.
The Doctor and Yaz take Schwarz back to 1605, allowing him to face up to his past self. The two Schwarzes quietly cry at understanding the pain they hold, and the younger Schwarz makes his mind up, blowing out his lit fuse. The elder Schwarz and his future timeline immediately vanish, and the curse is lifted. Stepping out of the TARDIS to see the next morning, Yaz and Schwarz's scars heal as Schwarz steps away, promising to learn from the time travellers in the time he has left. The Doctor apologises for how their trip away ended up and decide against meeting up with James I again.
Back in the Sheffield alleyway a few hours later, Yaz's memories fade away and she gets an idea. She explains to the gunman that she will close her eyes for ten seconds to allow him to either shoot her or escape. He chooses the latter option, and the Doctor emerges from the shadows, having watched the ordeal while checking that history had returned to normal. Satisfied, she and Yaz decide to watch the fireworks together, in awe of the power of the black powder.
- The Gunpowder Plot is a fixed point in time.
- Yaz was working on Bonfire Night when the Doctor picked her up, dealing with rogue fireworks and frightened dogs.
- The TARDIS' translation circuit automatically registers anything it has not heard before.
- One of the illustrations for part one of this story features the St John Ambulance badge on the door of the Doctor's TARDIS, despite it not appearing on the Thirteenth Doctor's TARDIS design.
- Yaz recalls their encounter with King James I twenty years in his future. (TV: The Witchfinders)
- The Thirteenth Doctor mentions being shot at by CyberMondans (TV: World Enough and Time, The Doctor Falls) and San Francisco gangs, on which occasion the attempt to take the bullet out "didn't go so well". (TV: Doctor Who)